1 <!doctype linuxdoc system> <!-- -*- text-mode -*- -->
4 <title>ca65 Users Guide
5 <author><url url="mailto:uz@cc65.org" name="Ullrich von Bassewitz">,<newline>
6 <url url="mailto:greg.king5@verizon.net" name="Greg King">
9 ca65 is a powerful macro assembler for the 6502, 65C02, and 65816 CPUs. It is
10 used as a companion assembler for the cc65 crosscompiler, but it may also be
11 used as a standalone product.
14 <!-- Table of contents -->
17 <!-- Begin the document -->
21 ca65 is a replacement for the ra65 assembler that was part of the cc65 C
22 compiler, originally developed by John R. Dunning. I had some problems with
23 ra65 and the copyright does not permit some things which I wanted to be
24 possible, so I decided to write a completely new assembler/linker/archiver
25 suite for the cc65 compiler. ca65 is part of this suite.
27 Some parts of the assembler (code generation and some routines for symbol
28 table handling) are taken from an older crossassembler named a816 written
29 by me a long time ago.
32 <sect1>Design criteria<p>
34 Here's a list of the design criteria, that I considered important for the
39 <item> The assembler must support macros. Macros are not essential, but they
40 make some things easier, especially when you use the assembler in the
41 backend of a compiler.
42 <item> The assembler must support the newer 65C02 and 65816 CPUs. I have been
43 thinking about a 65816 backend for the C compiler, and even my old
44 a816 assembler had support for these CPUs, so this wasn't really a
46 <item> The assembler must produce relocatable code. This is necessary for the
47 compiler support, and it is more convenient.
48 <item> Conditional assembly must be supported. This is a must for bigger
49 projects written in assembler (like Elite128).
50 <item> The assembler must support segments, and it must support more than
51 three segments (this is the count, most other assemblers support).
52 Having more than one code segments helps developing code for systems
53 with a divided ROM area (like the C64).
54 <item> The linker must be able to resolve arbitrary expressions. It should
55 be able to get things like
62 <item> True lexical nesting for symbols. This is very convenient for larger
64 <item> "Cheap" local symbols without lexical nesting for those quick, late
66 <item> I liked the idea of "options" as Anre Fachats .o65 format has it, so I
67 introduced the concept into the object file format use by the new cc65
69 <item> The assembler will be a one pass assembler. There was no real need for
70 this decision, but I've written several multipass assemblers, and it
71 started to get boring. A one pass assembler needs much more elaborated
72 data structures, and because of that it's much more fun:-)
73 <item> Non-GPLed code that may be used in any project without restrictions or
74 fear of "GPL infecting" other code.
82 <sect1>Command line option overview<p>
84 The assembler accepts the following options:
87 ---------------------------------------------------------------------------
88 Usage: ca65 [options] file
90 -D name[=value] Define a symbol
91 -I dir Set an include directory search path
92 -U Mark unresolved symbols as import
93 -V Print the assembler version
94 -W n Set warning level n
96 -g Add debug info to object file
98 -i Ignore case of symbols
99 -l name Create a listing file if assembly was ok
100 -mm model Set the memory model
101 -o name Name the output file
103 -t sys Set the target system
104 -v Increase verbosity
107 --auto-import Mark unresolved symbols as import
108 --bin-include-dir dir Set a search path for binary includes
109 --cpu type Set cpu type
110 --create-dep name Create a make dependency file
111 --create-full-dep name Create a full make dependency file
113 --debug-info Add debug info to object file
114 --feature name Set an emulation feature
115 --help Help (this text)
116 --ignore-case Ignore case of symbols
117 --include-dir dir Set an include directory search path
118 --large-alignment Don't warn about large alignments
119 --listing name Create a listing file if assembly was ok
120 --list-bytes n Maximum number of bytes per listing line
121 --memory-model model Set the memory model
122 --pagelength n Set the page length for the listing
123 --relax-checks Relax some checks (see docs)
124 --smart Enable smart mode
125 --target sys Set the target system
126 --verbose Increase verbosity
127 --version Print the assembler version
128 ---------------------------------------------------------------------------
132 <sect1>Command line options in detail<p>
134 Here is a description of all the command line options:
138 <label id="option--bin-include-dir">
139 <tag><tt>--bin-include-dir dir</tt></tag>
141 Name a directory which is searched for binary include files. The option
142 may be used more than once to specify more than one directory to search. The
143 current directory is always searched first before considering any
144 additional directories. See also the section about <ref id="search-paths"
145 name="search paths">.
148 <label id="option--cpu">
149 <tag><tt>--cpu type</tt></tag>
151 Set the default for the CPU type. The option takes a parameter, which
154 6502, 6502X, 65SC02, 65C02, 65816, sweet16, HuC6280, 4510
157 <label id="option-create-dep">
158 <tag><tt>--create-dep name</tt></tag>
160 Tells the assembler to generate a file containing the dependency list for
161 the assembled module in makefile syntax. The output is written to a file
162 with the given name. The output does not include files passed via debug
163 information to the assembler.
166 <label id="option-create-full-dep">
167 <tag><tt>--create-full-dep name</tt></tag>
169 Tells the assembler to generate a file containing the dependency list for
170 the assembled module in makefile syntax. The output is written to a file
171 with the given name. The output does include files passed via debug
172 information to the assembler.
175 <tag><tt>-d, --debug</tt></tag>
177 Enables debug mode, something that should not be needed for mere
181 <label id="option--feature">
182 <tag><tt>--feature name</tt></tag>
184 Enable an emulation feature. This is identical as using <tt/.FEATURE/
185 in the source with two exceptions: Feature names must be lower case, and
186 each feature must be specified by using an extra <tt/--feature/ option,
187 comma separated lists are not allowed.
189 See the discussion of the <tt><ref id=".FEATURE" name=".FEATURE"></tt>
190 command for a list of emulation features.
193 <label id="option-g">
194 <tag><tt>-g, --debug-info</tt></tag>
196 When this option (or the equivalent control command <tt/.DEBUGINFO/) is
197 used, the assembler will add a section to the object file that contains
198 all symbols (including local ones) together with the symbol values and
199 source file positions. The linker will put these additional symbols into
200 the VICE label file, so even local symbols can be seen in the VICE
204 <label id="option-h">
205 <tag><tt>-h, --help</tt></tag>
207 Print the short option summary shown above.
210 <label id="option-i">
211 <tag><tt>-i, --ignore-case</tt></tag>
213 This option makes the assembler case insensitive on identifiers and labels.
214 This option will override the default, but may itself be overridden by the
215 <tt><ref id=".CASE" name=".CASE"></tt> control command.
218 <label id="option-l">
219 <tag><tt>-l name, --listing name</tt></tag>
221 Generate an assembler listing with the given name. A listing file will
222 never be generated in case of assembly errors.
225 <label id="option--large-alignment">
226 <tag><tt>--large-alignment</tt></tag>
228 Disable warnings about a large combined alignment. See the discussion of the
229 <tt><ref id=".ALIGN" name=".ALIGN"></tt> directive for futher information.
232 <label id="option--list-bytes">
233 <tag><tt>--list-bytes n</tt></tag>
235 Set the maximum number of bytes printed in the listing for one line of
236 input. See the <tt><ref id=".LISTBYTES" name=".LISTBYTES"></tt> directive
237 for more information. The value zero can be used to encode an unlimited
238 number of printed bytes.
241 <label id="option-mm">
242 <tag><tt>-mm model, --memory-model model</tt></tag>
244 Define the default memory model. Possible model specifiers are near, far and
248 <label id="option-o">
249 <tag><tt>-o name</tt></tag>
251 The default output name is the name of the input file with the extension
252 replaced by ".o". If you don't like that, you may give another name with
253 the -o option. The output file will be placed in the same directory as
254 the source file, or, if -o is given, the full path in this name is used.
257 <label id="option--pagelength">
258 <tag><tt>--pagelength n</tt></tag>
260 sets the length of a listing page in lines. See the <tt><ref
261 id=".PAGELENGTH" name=".PAGELENGTH"></tt> directive for more information.
264 <label id="option--relax-checks">
265 <tag><tt>--relax-checks</tt></tag>
267 Relax some checks done by the assembler. This will allow code that is an
268 error in most cases and flagged as such by the assembler, but can be valid
269 in special situations.
273 <item>Short branches between two different segments.
274 <item>Byte sized address loads where the address is not a zeropage address.
278 <label id="option-s">
279 <tag><tt>-s, --smart-mode</tt></tag>
281 In smart mode (enabled by -s or the <tt><ref id=".SMART" name=".SMART"></tt>
282 pseudo instruction) the assembler will track usage of the <tt/REP/ and
283 <tt/SEP/ instructions in 65816 mode and update the operand sizes
284 accordingly. If the operand of such an instruction cannot be evaluated by
285 the assembler (for example, because the operand is an imported symbol), a
288 Beware: Since the assembler cannot trace the execution flow this may
289 lead to false results in some cases. If in doubt, use the .ixx and .axx
290 instructions to tell the assembler about the current settings. Smart
291 mode is off by default.
294 <label id="option-t">
295 <tag><tt>-t sys, --target sys</tt></tag>
297 Set the target system. This will enable translation of character strings and
298 character constants into the character set of the target platform. The
299 default for the target system is "none", which means that no translation
300 will take place. The assembler supports the same target systems as the
301 compiler, see there for a list.
303 Depending on the target, the default CPU type is also set. This can be
304 overriden by using the <tt/<ref id="option--cpu" name="--cpu">/ option.
307 <label id="option-v">
308 <tag><tt>-v, --verbose</tt></tag>
310 Increase the assembler verbosity. Usually only needed for debugging
311 purposes. You may use this option more than one time for even more
315 <label id="option-D">
316 <tag><tt>-D</tt></tag>
318 This option allows you to define symbols on the command line. Without a
319 value, the symbol is defined with the value zero. When giving a value,
320 you may use the '$' prefix for hexadecimal symbols. Please note
321 that for some operating systems, '$' has a special meaning, so
322 you may have to quote the expression.
325 <label id="option-I">
326 <tag><tt>-I dir, --include-dir dir</tt></tag>
328 Name a directory which is searched for include files. The option may be
329 used more than once to specify more than one directory to search. The
330 current directory is always searched first before considering any
331 additional directories. See also the section about <ref id="search-paths"
332 name="search paths">.
335 <label id="option-U">
336 <tag><tt>-U, --auto-import</tt></tag>
338 Mark symbols that are not defined in the sources as imported symbols. This
339 should be used with care since it delays error messages about typos and such
340 until the linker is run. The compiler uses the equivalent of this switch
341 (<tt><ref id=".AUTOIMPORT" name=".AUTOIMPORT"></tt>) to enable auto imported
342 symbols for the runtime library. However, the compiler is supposed to
343 generate code that runs through the assembler without problems, something
344 which is not always true for assembler programmers.
347 <label id="option-V">
348 <tag><tt>-V, --version</tt></tag>
350 Print the version number of the assembler. If you send any suggestions
351 or bugfixes, please include the version number.
354 <label id="option-W">
355 <tag><tt>-Wn</tt></tag>
357 Set the warning level for the assembler. Using -W2 the assembler will
358 even warn about such things like unused imported symbols. The default
359 warning level is 1, and it would probably be silly to set it to
367 <sect>Search paths<label id="search-paths"><p>
369 Normal include files are searched in the following places:
372 <item>The current file's directory.
373 <item>Any directory added with the <tt/<ref id="option-I" name="-I">/ option
375 <item>The value of the environment variable <tt/CA65_INC/ if it is defined.
376 <item>A subdirectory named <tt/asminc/ of the directory defined in the
377 environment variable <tt/CC65_HOME/, if it is defined.
378 <item>An optionally compiled-in directory.
381 Binary include files are searched in the following places:
384 <item>The current file's directory.
385 <item>Any directory added with the <tt/<ref id="option--bin-include-dir"
386 name="--bin-include-dir">/ option on the command line.
391 <sect>Input format<p>
393 <sect1>Assembler syntax<p>
395 The assembler accepts the standard 6502/65816 assembler syntax. One line may
396 contain a label (which is identified by a colon), and, in addition to the
397 label, an assembler mnemonic, a macro, or a control command (see section <ref
398 id="control-commands" name="Control Commands"> for supported control
399 commands). Alternatively, the line may contain a symbol definition using
400 the '=' token. Everything after a semicolon is handled as a comment (that is,
403 Here are some examples for valid input lines:
406 Label: ; A label and a comment
407 lda #$20 ; A 6502 instruction plus comment
408 L1: ldx #$20 ; Same with label
409 L2: .byte "Hello world" ; Label plus control command
410 mymac $20 ; Macro expansion
411 MySym = 3*L1 ; Symbol definition
412 MaSym = Label ; Another symbol
415 The assembler accepts
418 <item>all valid 6502 mnemonics when in 6502 mode (the default or after the
419 <tt><ref id=".P02" name=".P02"></tt> command was given).
420 <item>all valid 6502 mnemonics plus a set of illegal instructions when in
421 <ref id="6502X-mode" name="6502X mode">.
422 <item>all valid 65SC02 mnemonics when in 65SC02 mode (after the
423 <tt><ref id=".PSC02" name=".PSC02"></tt> command was given).
424 <item>all valid 65C02 mnemonics when in 65C02 mode (after the
425 <tt><ref id=".PC02" name=".PC02"></tt> command was given).
426 <item>all valid 65816 mnemonics when in 65816 mode (after the
427 <tt><ref id=".P816" name=".P816"></tt> command was given).
428 <item>all valid 4510 mnemonics when in 4510 mode (after the
429 <tt><ref id=".P4510" name=".P4510"></tt> command was given).
435 In 65816 mode, several aliases are accepted, in addition to the official
439 <item><tt>CPA</tt> is an alias for <tt>CMP</tt>
440 <item><tt>DEA</tt> is an alias for <tt>DEC A</tt>
441 <item><tt>INA</tt> is an alias for <tt>INC A</tt>
442 <item><tt>SWA</tt> is an alias for <tt>XBA</tt>
443 <item><tt>TAD</tt> is an alias for <tt>TCD</tt>
444 <item><tt>TAS</tt> is an alias for <tt>TCS</tt>
445 <item><tt>TDA</tt> is an alias for <tt>TDC</tt>
446 <item><tt>TSA</tt> is an alias for <tt>TSC</tt>
450 <sect1>6502X mode<label id="6502X-mode"><p>
452 6502X mode is an extension to the normal 6502 mode. In this mode, several
453 mnemonics for illegal instructions of the NMOS 6502 CPUs are accepted. Since
454 these instructions are illegal, there are no official mnemonics for them. The
455 unofficial ones are taken from <url
456 url="http://www.oxyron.de/html/opcodes02.html">. Please note that only the
457 ones marked as "stable" are supported. The following table uses information
458 from the mentioned web page, for more information, see there.
461 <item><tt>ALR: A:=(A and #{imm})/2;</tt>
462 <item><tt>ANC: A:=A and #{imm};</tt> Generates opcode $0B.
463 <item><tt>ARR: A:=(A and #{imm})/2;</tt>
464 <item><tt>AXS: X:=A and X-#{imm};</tt>
465 <item><tt>DCP: {adr}:={adr}-1; A-{adr};</tt>
466 <item><tt>ISC: {adr}:={adr}+1; A:=A-{adr};</tt>
467 <item><tt>LAS: A,X,S:={adr} and S;</tt>
468 <item><tt>LAX: A,X:={adr};</tt>
469 <item><tt>RLA: {adr}:={adr}rol; A:=A and {adr};</tt>
470 <item><tt>RRA: {adr}:={adr}ror; A:=A adc {adr};</tt>
471 <item><tt>SAX: {adr}:=A and X;</tt>
472 <item><tt>SLO: {adr}:={adr}*2; A:=A or {adr};</tt>
473 <item><tt>SRE: {adr}:={adr}/2; A:=A xor {adr};</tt>
479 The 4510 is a microcontroller that is the core of the Commodore C65 aka C64DX.
480 It contains among other functions a slightly modified 65CE02/4502 CPU, to allow
481 address mapping for 20 bits of address space (1 megabyte addressable area).
482 As compared to the description of the CPU in the
483 <url url="http://www.zimmers.net/anonftp/pub/cbm/c65/c65manualupdated.txt.gz"
484 name="C65 System Specification">
485 <url url="https://raw.githubusercontent.com/MEGA65/c65-specifications/master/c65manualupdated.txt"
486 name="(updated version)"> uses these changes:
488 <item><tt>LDA (d,SP),Y</tt> may also be written as <tt>LDA (d,S),Y</tt>
489 (matching the 65816 notataion).
490 <item>All branch instruction allow now 16 bit offsets. To use a 16 bit
491 branch you have to prefix these with an "L" (e.g. "<tt>LBNE</tt>" instead of
492 "<tt>BNE</tt>"). This might change at a later implementation of the assembler.
494 For more information about the Commodore C65/C64DX and the 4510 CPU, see
495 <url url="http://www.zimmers.net/anonftp/pub/cbm/c65/"> and
496 <url url="https://en.wikipedia.org/wiki/Commodore_65" name="Wikipedia">.
499 <sect1>sweet16 mode<label id="sweet16-mode"><p>
501 SWEET 16 is an interpreter for a pseudo 16 bit CPU written by Steve Wozniak
502 for the Apple ][ machines. It is available in the Apple ][ ROM. ca65 can
503 generate code for this pseudo CPU when switched into sweet16 mode. The
504 following is special in sweet16 mode:
508 <item>The '@' character denotes indirect addressing and is no longer available
509 for cheap local labels. If you need cheap local labels, you will have to
510 switch to another lead character using the <tt/<ref id=".LOCALCHAR"
511 name=".LOCALCHAR">/ command.
513 <item>Registers are specified using <tt/R0/ .. <tt/R15/. In sweet16 mode,
514 these identifiers are reserved words.
518 Please note that the assembler does neither supply the interpreter needed for
519 SWEET 16 code, nor the zero page locations needed for the SWEET 16 registers,
520 nor does it call the interpreter. All this must be done by your program. Apple
521 ][ programmers do probably know how to use sweet16 mode.
523 For more information about SWEET 16, see
524 <url url="http://www.6502.org/source/interpreters/sweet16.htm">.
527 <sect1>Number format<p>
529 For literal values, the assembler accepts the widely used number formats: A
530 preceding '$' or a trailing 'h' denotes a hex value, a preceding '%'
531 denotes a binary value, and a bare number is interpreted as a decimal. There
532 are currently no octal values and no floats.
535 <sect1>Conditional assembly<p>
537 Please note that when using the conditional directives (<tt/.IF/ and friends),
538 the input must consist of valid assembler tokens, even in <tt/.IF/ branches
539 that are not assembled. The reason for this behaviour is that the assembler
540 must still be able to detect the ending tokens (like <tt/.ENDIF/), so
541 conversion of the input stream into tokens still takes place. As a consequence
542 conditional assembly directives may <bf/not/ be used to prevent normal text
543 (used as a comment or similar) from being assembled. <p>
549 <sect1>Expression evaluation<p>
551 All expressions are evaluated with (at least) 32 bit precision. An
552 expression may contain constant values and any combination of internal and
553 external symbols. Expressions that cannot be evaluated at assembly time
554 are stored inside the object file for evaluation by the linker.
555 Expressions referencing imported symbols must always be evaluated by the
559 <sect1>Size of an expression result<p>
561 Sometimes, the assembler must know about the size of the value that is the
562 result of an expression. This is usually the case, if a decision has to be
563 made, to generate a zero page or an absolute memory references. In this
564 case, the assembler has to make some assumptions about the result of an
568 <item> If the result of an expression is constant, the actual value is
569 checked to see if it's a byte sized expression or not.
570 <item> If the expression is explicitly casted to a byte sized expression by
571 one of the '>', '<' or '^' operators, it is a byte expression.
572 <item> If this is not the case, and the expression contains a symbol,
573 explicitly declared as zero page symbol (by one of the .importzp or
574 .exportzp instructions), then the whole expression is assumed to be
576 <item> If the expression contains symbols that are not defined, and these
577 symbols are local symbols, the enclosing scopes are searched for a
578 symbol with the same name. If one exists and this symbol is defined,
579 its attributes are used to determine the result size.
580 <item> In all other cases the expression is assumed to be word sized.
583 Note: If the assembler is not able to evaluate the expression at assembly
584 time, the linker will evaluate it and check for range errors as soon as
588 <sect1>Boolean expressions<p>
590 In the context of a boolean expression, any non zero value is evaluated as
591 true, any other value to false. The result of a boolean expression is 1 if
592 it's true, and zero if it's false. There are boolean operators with extreme
593 low precedence with version 2.x (where x > 0). The <tt/.AND/ and <tt/.OR/
594 operators are shortcut operators. That is, if the result of the expression is
595 already known, after evaluating the left hand side, the right hand side is
599 <sect1>Constant expressions<p>
601 Sometimes an expression must evaluate to a constant without looking at any
602 further input. One such example is the <tt/<ref id=".IF" name=".IF">/ command
603 that decides if parts of the code are assembled or not. An expression used in
604 the <tt/.IF/ command cannot reference a symbol defined later, because the
605 decision about the <tt/.IF/ must be made at the point when it is read. If the
606 expression used in such a context contains only constant numerical values,
607 there is no problem. When unresolvable symbols are involved it may get harder
608 for the assembler to determine if the expression is actually constant, and it
609 is even possible to create expressions that aren't recognized as constant.
610 Simplifying the expressions will often help.
612 In cases where the result of the expression is not needed immediately, the
613 assembler will delay evaluation until all input is read, at which point all
614 symbols are known. So using arbitrary complex constant expressions is no
615 problem in most cases.
619 <sect1>Available operators<label id="operators"><p>
623 <bf/Operator/| <bf/Description/| <bf/Precedence/@<hline>
624 | Built-in string functions| 0@
626 | Built-in pseudo-variables| 1@
627 | Built-in pseudo-functions| 1@
628 +| Unary positive| 1@
629 -| Unary negative| 1@
631 .BITNOT| Unary bitwise not| 1@
633 .LOBYTE| Unary low-byte operator| 1@
635 .HIBYTE| Unary high-byte operator| 1@
637 .BANKBYTE| Unary bank-byte operator| 1@
639 *| Multiplication| 2@
641 .MOD| Modulo operator| 2@
643 .BITAND| Bitwise and| 2@
645 .BITXOR| Binary bitwise xor| 2@
647 .SHL| Shift-left operator| 2@
649 .SHR| Shift-right operator| 2@
651 +| Binary addition| 3@
652 -| Binary subtraction| 3@
654 .BITOR| Bitwise or| 3@
656 = | Compare operator (equal)| 4@
657 <>| Compare operator (not equal)| 4@
658 <| Compare operator (less)| 4@
659 >| Compare operator (greater)| 4@
660 <=| Compare operator (less or equal)| 4@
661 >=| Compare operator (greater or equal)| 4@
664 .AND| Boolean and| 5@
665 .XOR| Boolean xor| 5@
667 ||<newline>
671 .NOT| Boolean not| 7@<hline>
673 <caption>Available operators, sorted by precedence
676 To force a specific order of evaluation, parentheses may be used, as usual.
680 <sect>Symbols and labels<p>
682 A symbol or label is an identifier that starts with a letter and is followed
683 by letters and digits. Depending on some features enabled (see
684 <tt><ref id="at_in_identifiers" name="at_in_identifiers"></tt>,
685 <tt><ref id="dollar_in_identifiers" name="dollar_in_identifiers"></tt> and
686 <tt><ref id="leading_dot_in_identifiers" name="leading_dot_in_identifiers"></tt>)
687 other characters may be present. Use of identifiers consisting of a single
688 character will not work in all cases, because some of these identifiers are
689 reserved keywords (for example "A" is not a valid identifier for a label,
690 because it is the keyword for the accumulator).
692 The assembler allows you to use symbols instead of naked values to make
693 the source more readable. There are a lot of different ways to define and
694 use symbols and labels, giving a lot of flexibility.
696 <sect1>Numeric constants<p>
698 Numeric constants are defined using the equal sign or the label assignment
699 operator. After doing
705 may use the symbol "two" in every place where a number is expected, and it is
706 evaluated to the value 2 in this context. The label assignment operator is
707 almost identical, but causes the symbol to be marked as a label, so it may be
708 handled differently in a debugger:
714 The right side can of course be an expression:
721 <label id="variables">
722 <sect1>Numeric variables<p>
724 Within macros and other control structures (<tt><ref id=".REPEAT"
725 name=".REPEAT"></tt>, ...) it is sometimes useful to have some sort of
726 variable. This can be achieved by the <tt>.SET</tt> operator. It creates a
727 symbol that may get assigned a different value later:
731 lda #four ; Loads 4 into A
733 lda #four ; Loads 3 into A
736 Since the value of the symbol can change later, it must be possible to
737 evaluate it when used (no delayed evaluation as with normal symbols). So the
738 expression used as the value must be constant.
740 Following is an example for a macro that generates a different label each time
741 it is used. It uses the <tt><ref id=".SPRINTF" name=".SPRINTF"></tt> function
742 and a numeric variable named <tt>lcount</tt>.
745 .lcount .set 0 ; Initialize the counter
748 .ident (.sprintf ("L%04X", lcount)):
749 lcount .set lcount + 1
754 <sect1>Standard labels<p>
756 A label is defined by writing the name of the label at the start of the line
757 (before any instruction mnemonic, macro or pseudo directive), followed by a
758 colon. This will declare a symbol with the given name and the value of the
759 current program counter.
762 <sect1>Local labels and symbols<p>
764 Using the <tt><ref id=".PROC" name=".PROC"></tt> directive, it is possible to
765 create regions of code where the names of labels and symbols are local to this
766 region. They are not known outside of this region and cannot be accessed from
767 there. Such regions may be nested like PROCEDUREs in Pascal.
769 See the description of the <tt><ref id=".PROC" name=".PROC"></tt>
770 directive for more information.
773 <sect1>Cheap local labels<p>
775 Cheap local labels are defined like standard labels, but the name of the
776 label must begin with a special symbol (usually '@', but this can be
777 changed by the <tt><ref id=".LOCALCHAR" name=".LOCALCHAR"></tt>
780 Cheap local labels are visible only between two non cheap labels. As soon as a
781 standard symbol is encountered (this may also be a local symbol if inside a
782 region defined with the <tt><ref id=".PROC" name=".PROC"></tt> directive), the
783 cheap local symbol goes out of scope.
785 You may use cheap local labels as an easy way to reuse common label
786 names like "Loop". Here is an example:
789 Clear: lda #$00 ; Global label
791 @Loop: sta Mem,y ; Local label
795 Sub: ... ; New global label
796 bne @Loop ; ERROR: Unknown identifier!
799 <sect1>Unnamed labels<p>
801 If you really want to write messy code, there are also unnamed labels. These
802 labels do not have a name (you guessed that already, didn't you?). A colon is
803 used to mark the absence of the name.
805 Unnamed labels may be accessed by using the colon plus several minus or plus
806 characters as a label designator. Using the '-' characters will create a back
807 reference (use the n'th label backwards), using '+' will create a forward
808 reference (use the n'th label in forward direction). An example will help to
831 As you can see from the example, unnamed labels will make even short
832 sections of code hard to understand, because you have to count labels
833 to find branch targets (this is the reason why I for my part do
834 prefer the "cheap" local labels). Nevertheless, unnamed labels are
835 convenient in some situations, so it's your decision.
837 <em/Note:/ <ref id="scopes" name="Scopes"> organize named symbols, not
838 unnamed ones, so scopes don't have an effect on unnamed labels.
842 <sect1>Using macros to define labels and constants<p>
844 While there are drawbacks with this approach, it may be handy in a few rare
845 situations. Using <tt><ref id=".DEFINE" name=".DEFINE"></tt>, it is possible
846 to define symbols or constants that may be used elsewhere. One of the
847 advantages is that you can use it to define string constants (this is not
848 possible with the other symbol types).
850 Please note: <tt/.DEFINE/ style macros do token replacements on a low level,
851 so the names do not adhere to scoping, diagnostics may be misleading, there
852 are no symbols to look up in the map file, and there is no debug info.
853 Especially the first problem in the list can lead to very nasty programming
854 errors. Because of these problems, the general advice is, <bf/NOT/ do use
855 <tt/.DEFINE/ if you don't have to.
861 .DEFINE version "SOS V2.3"
863 four = two * two ; Ok
866 .PROC ; Start local scope
867 two = 3 ; Will give "2 = 3" - invalid!
872 <sect1>Symbols and <tt>.DEBUGINFO</tt><p>
874 If <tt><ref id=".DEBUGINFO" name=".DEBUGINFO"></tt> is enabled (or <ref
875 id="option-g" name="-g"> is given on the command line), global, local and
876 cheap local labels are written to the object file and will be available in the
877 symbol file via the linker. Unnamed labels are not written to the object file,
878 because they don't have a name which would allow to access them.
882 <sect>Scopes<label id="scopes"><p>
884 ca65 implements several sorts of scopes for symbols.
886 <sect1>Global scope<p>
888 All (non cheap local) symbols that are declared outside of any nested scopes
892 <sect1>Cheap locals<p>
894 A special scope is the scope for cheap local symbols. It lasts from one non
895 local symbol to the next one, without any provisions made by the programmer.
896 All other scopes differ in usage but use the same concept internally.
899 <sect1>Generic nested scopes<p>
901 A nested scoped for generic use is started with <tt/<ref id=".SCOPE"
902 name=".SCOPE">/ and closed with <tt/<ref id=".ENDSCOPE" name=".ENDSCOPE">/.
903 The scope can have a name, in which case it is accessible from the outside by
904 using <ref id="scopesyntax" name="explicit scopes">. If the scope does not
905 have a name, all symbols created within the scope are local to the scope, and
906 aren't accessible from the outside.
908 A nested scope can access symbols from the local or from enclosing scopes by
909 name without using explicit scope names. In some cases there may be
910 ambiguities, for example if there is a reference to a local symbol that is not
911 yet defined, but a symbol with the same name exists in outer scopes:
923 In the example above, the <tt/lda/ instruction will load the value 3 into the
924 accumulator, because <tt/foo/ is redefined in the scope. However:
936 Here, <tt/lda/ will still load from <tt/$12,x/, but since it is unknown to the
937 assembler that <tt/foo/ is a zeropage symbol when translating the instruction,
938 absolute mode is used instead. In fact, the assembler will not use absolute
939 mode by default, but it will search through the enclosing scopes for a symbol
940 with the given name. If one is found, the address size of this symbol is used.
941 This may lead to errors:
953 In this case, when the assembler sees the symbol <tt/foo/ in the <tt/lda/
954 instruction, it will search for an already defined symbol <tt/foo/. It will
955 find <tt/foo/ in scope <tt/outer/, and a close look reveals that it is a
956 zeropage symbol. So the assembler will use zeropage addressing mode. If
957 <tt/foo/ is redefined later in scope <tt/inner/, the assembler tries to change
958 the address in the <tt/lda/ instruction already translated, but since the new
959 value needs absolute addressing mode, this fails, and an error message "Range
962 Of course the most simple solution for the problem is to move the definition
963 of <tt/foo/ in scope <tt/inner/ upwards, so it precedes its use. There may be
964 rare cases when this cannot be done. In these cases, you can use one of the
965 address size override operators:
977 This will cause the <tt/lda/ instruction to be translated using absolute
978 addressing mode, which means changing the symbol reference later does not
982 <sect1>Nested procedures<p>
984 A nested procedure is created by use of <tt/<ref id=".PROC" name=".PROC">/. It
985 differs from a <tt/<ref id=".SCOPE" name=".SCOPE">/ in that it must have a
986 name, and a it will introduce a symbol with this name in the enclosing scope.
995 is actually the same as
1004 This is the reason why a procedure must have a name. If you want a scope
1005 without a name, use <tt/<ref id=".SCOPE" name=".SCOPE">/.
1007 <em/Note:/ As you can see from the example above, scopes and symbols live in
1008 different namespaces. There can be a symbol named <tt/foo/ and a scope named
1009 <tt/foo/ without any conflicts (but see the section titled <ref
1010 id="scopesearch" name=""Scope search order"">).
1013 <sect1>Structs, unions and enums<p>
1015 Structs, unions and enums are explained in a <ref id="structs" name="separate
1016 section">, I do only cover them here, because if they are declared with a
1017 name, they open a nested scope, similar to <tt/<ref id=".SCOPE"
1018 name=".SCOPE">/. However, when no name is specified, the behaviour is
1019 different: In this case, no new scope will be opened, symbols declared within
1020 a struct, union, or enum declaration will then be added to the enclosing scope
1024 <sect1>Explicit scope specification<label id="scopesyntax"><p>
1026 Accessing symbols from other scopes is possible by using an explicit scope
1027 specification, provided that the scope where the symbol lives in has a name.
1028 The namespace token (<tt/::/) is used to access other scopes:
1036 lda foo::bar ; Access foo in scope bar
1039 The only way to deny access to a scope from the outside is to declare a scope
1040 without a name (using the <tt/<ref id=".SCOPE" name=".SCOPE">/ command).
1042 A special syntax is used to specify the global scope: If a symbol or scope is
1043 preceded by the namespace token, the global scope is searched:
1050 lda #::bar ; Access the global bar (which is 3)
1055 <sect1>Scope search order<label id="scopesearch"><p>
1057 The assembler searches for a scope in a similar way as for a symbol. First, it
1058 looks in the current scope, and then it walks up the enclosing scopes until
1061 However, one important thing to note when using explicit scope syntax is, that
1062 a symbol may be accessed before it is defined, but a scope may <bf/not/ be
1063 used without a preceding definition. This means that in the following
1072 lda #foo::bar ; Will load 3, not 2!
1079 the reference to the scope <tt/foo/ will use the global scope, and not the
1080 local one, because the local one is not visible at the point where it is
1083 Things get more complex if a complete chain of scopes is specified:
1094 lda #outer::inner::bar ; 1
1106 When <tt/outer::inner::bar/ is referenced in the <tt/lda/ instruction, the
1107 assembler will first search in the local scope for a scope named <tt/outer/.
1108 Since none is found, the enclosing scope (<tt/another/) is checked. There is
1109 still no scope named <tt/outer/, so scope <tt/foo/ is checked, and finally
1110 scope <tt/outer/ is found. Within this scope, <tt/inner/ is searched, and in
1111 this scope, the assembler looks for a symbol named <tt/bar/.
1113 Please note that once the anchor scope is found, all following scopes
1114 (<tt/inner/ in this case) are expected to be found exactly in this scope. The
1115 assembler will search the scope tree only for the first scope (if it is not
1116 anchored in the root scope). Starting from there on, there is no flexibility,
1117 so if the scope named <tt/outer/ found by the assembler does not contain a
1118 scope named <tt/inner/, this would be an error, even if such a pair does exist
1119 (one level up in global scope).
1121 Ambiguities that may be introduced by this search algorithm may be removed by
1122 anchoring the scope specification in the global scope. In the example above,
1123 if you want to access the "other" symbol <tt/bar/, you would have to write:
1134 lda #::outer::inner::bar ; 2
1147 <sect>Address sizes and memory models<label id="address-sizes"><p>
1149 <sect1>Address sizes<p>
1151 ca65 assigns each segment and each symbol an address size. This is true, even
1152 if the symbol is not used as an address. You may also think of a value range
1153 of the symbol instead of an address size.
1155 Possible address sizes are:
1158 <item>Zeropage or direct (8 bits)
1159 <item>Absolute (16 bits)
1161 <item>Long (32 bits)
1164 Since the assembler uses default address sizes for the segments and symbols,
1165 it is usually not necessary to override the default behaviour. In cases, where
1166 it is necessary, the following keywords may be used to specify address sizes:
1169 <item>DIRECT, ZEROPAGE or ZP for zeropage addressing (8 bits).
1170 <item>ABSOLUTE, ABS or NEAR for absolute addressing (16 bits).
1171 <item>FAR for far addressing (24 bits).
1172 <item>LONG or DWORD for long addressing (32 bits).
1176 <sect1>Address sizes of segments<p>
1178 The assembler assigns an address size to each segment. Since the
1179 representation of a label within this segment is "segment start + offset",
1180 labels will inherit the address size of the segment they are declared in.
1182 The address size of a segment may be changed, by using an optional address
1183 size modifier. See the <tt/<ref id=".SEGMENT" name="segment directive">/ for
1184 an explanation on how this is done.
1187 <sect1>Address sizes of symbols<p>
1189 The address size of a symbol can be specified with a prefix:
1192 <item>z: zeropage addressing (8 bits).
1193 <item>a: absolute addressing (16 bits).
1194 <item>f: far addressing (24 bits).
1197 The zeropage addressing override can be used to ensure the use of optimal
1198 zeropage instructions, or correct cases where the size isn't yet known
1199 due to the single-pass assembly model.
1201 The larger addressing overrides can be used to promote a smaller address
1202 to absolute or far addressing, instead of being automatically fit into
1203 a smaller addressing type.
1206 <sect1>Memory models<p>
1208 The default address size of a segment depends on the memory model used. Since
1209 labels inherit the address size from the segment they are declared in,
1210 changing the memory model is an easy way to change the address size of many
1216 <sect>Pseudo variables<label id="pseudo-variables"><p>
1218 Pseudo variables are readable in all cases, and in some special cases also
1221 <sect1><tt>*</tt><p>
1223 Reading this pseudo variable will return the program counter at the start
1224 of the current input line.
1226 Assignment to this variable is possible when <tt/<ref id=".FEATURE"
1227 name=".FEATURE pc_assignment">/ is used. Note: You should not use
1228 assignments to <tt/*/, use <tt/<ref id=".ORG" name=".ORG">/ instead.
1231 <sect1><tt>.ASIZE</tt><label id=".ASIZE"><p>
1233 Reading this pseudo variable will return the current size of the
1234 Accumulator in bits.
1236 For the 65816 instruction set .ASIZE will return either 8 or 16, depending
1237 on the current size of the operand in immediate accu addressing mode.
1239 For all other CPU instruction sets, .ASIZE will always return 8.
1244 ; Reverse Subtract with Accumulator
1257 See also: <tt><ref id=".ISIZE" name=".ISIZE"></tt>
1260 <sect1><tt>.CPU</tt><label id=".CPU"><p>
1262 Reading this pseudo variable will give a constant integer value that
1263 tells which CPU is currently enabled. It can also tell which instruction
1264 set the CPU is able to translate. The value read from the pseudo variable
1265 should be further examined by using one of the constants defined by the
1266 "cpu" macro package (see <tt/<ref id=".MACPACK" name=".MACPACK">/).
1268 It may be used to replace the .IFPxx pseudo instructions or to construct
1269 even more complex expressions.
1275 .if (.cpu .bitand CPU_ISET_65816)
1287 <sect1><tt>.ISIZE</tt><label id=".ISIZE"><p>
1289 Reading this pseudo variable will return the current size of the Index
1292 For the 65816 instruction set .ISIZE will return either 8 or 16, depending
1293 on the current size of the operand in immediate index addressing mode.
1295 For all other CPU instruction sets, .ISIZE will always return 8.
1297 See also: <tt><ref id=".ASIZE" name=".ASIZE"></tt>
1300 <sect1><tt>.PARAMCOUNT</tt><label id=".PARAMCOUNT"><p>
1302 This builtin pseudo variable is only available in macros. It is replaced by
1303 the actual number of parameters that were given in the macro invocation.
1308 .macro foo arg1, arg2, arg3
1309 .if .paramcount <> 3
1310 .error "Too few parameters for macro foo"
1316 See section <ref id="macros" name="Macros">.
1319 <sect1><tt>.TIME</tt><label id=".TIME"><p>
1321 Reading this pseudo variable will give a constant integer value that
1322 represents the current time in POSIX standard (as seconds since the
1325 It may be used to encode the time of translation somewhere in the created
1331 .dword .time ; Place time here
1335 <sect1><tt>.VERSION</tt><label id=".VERSION"><p>
1337 Reading this pseudo variable will give the assembler version according to
1338 the following formula:
1340 VER_MAJOR*$100 + VER_MINOR*$10
1342 It may be used to encode the assembler version or check the assembler for
1343 special features not available with older versions.
1347 Version 2.14 of the assembler will return $2E0 as numerical constant when
1348 reading the pseudo variable <tt/.VERSION/.
1352 <sect>Pseudo functions<label id="pseudo-functions"><p>
1354 Pseudo functions expect their arguments in parenthesis, and they have a result,
1355 either a string or an expression.
1358 <sect1><tt>.ADDRSIZE</tt><label id=".ADDRSIZE"><p>
1360 The <tt/.ADDRSIZE/ function is used to return the interal address size
1361 associated with a symbol. This can be helpful in macros when knowing the address
1362 size of symbol can help with custom instructions.
1368 .if .ADDRSIZE(foo) = 1
1369 ;do custom command based on zeropage addressing:
1371 .elseif .ADDRSIZE(foo) = 2
1372 ;do custom command based on absolute addressing:
1375 .elseif .ADDRSIZE(foo) = 0
1376 ; no address size defined for this symbol:
1377 .out .sprintf("Error, address size unknown for symbol %s", .string(foo))
1382 This command is new and must be enabled with the <tt/.FEATURE addrsize/ command.
1384 See: <tt><ref id=".FEATURE" name=".FEATURE"></tt>
1387 <sect1><tt>.BANK</tt><label id=".BANK"><p>
1389 The <tt/.BANK/ function is used to support systems with banked memory. The
1390 argument is an expression with exactly one segment reference - usually a
1391 label. The function result is the value of the <tt/bank/ attribute assigned
1392 to the run memory area of the segment. Please see the linker documentation
1393 for more information about memory areas and their attributes.
1395 The value of <tt/.BANK/ can be used to switch memory so that a memory bank
1396 containing specific data is available.
1398 The <tt/bank/ attribute is a 32 bit integer and so is the result of the
1399 <tt/.BANK/ function. You will have to use <tt><ref id=".LOBYTE"
1400 name=".LOBYTE"></tt> or similar functions to address just part of it.
1402 Please note that <tt/.BANK/ will always get evaluated in the link stage, so
1403 an expression containing <tt/.BANK/ can never be used where a constant known
1404 result is expected (for example with <tt/.RES/).
1421 .byte <.BANK (banked_func_1)
1424 .byte <.BANK (banked_func_2)
1430 <sect1><tt>.BANKBYTE</tt><label id=".BANKBYTE"><p>
1432 The function returns the bank byte (that is, bits 16-23) of its argument.
1433 It works identical to the '^' operator.
1435 See: <tt><ref id=".HIBYTE" name=".HIBYTE"></tt>,
1436 <tt><ref id=".LOBYTE" name=".LOBYTE"></tt>
1439 <sect1><tt>.BLANK</tt><label id=".BLANK"><p>
1441 Builtin function. The function evaluates its argument in braces and yields
1442 "false" if the argument is non blank (there is an argument), and "true" if
1443 there is no argument. The token list that makes up the function argument
1444 may optionally be enclosed in curly braces. This allows the inclusion of
1445 tokens that would otherwise terminate the list (the closing right
1446 parenthesis). The curly braces are not considered part of the list, a list
1447 just consisting of curly braces is considered to be empty.
1449 As an example, the <tt/.IFBLANK/ statement may be replaced by
1457 <sect1><tt>.CONCAT</tt><label id=".CONCAT"><p>
1459 Builtin string function. The function allows to concatenate a list of string
1460 constants separated by commas. The result is a string constant that is the
1461 concatenation of all arguments. This function is most useful in macros and
1462 when used together with the <tt/.STRING/ builtin function. The function may
1463 be used in any case where a string constant is expected.
1468 .include .concat ("myheader", ".", "inc")
1471 This is the same as the command
1474 .include "myheader.inc"
1478 <sect1><tt>.CONST</tt><label id=".CONST"><p>
1480 Builtin function. The function evaluates its argument in braces and
1481 yields "true" if the argument is a constant expression (that is, an
1482 expression that yields a constant value at assembly time) and "false"
1483 otherwise. As an example, the .IFCONST statement may be replaced by
1490 <sect1><tt>.HIBYTE</tt><label id=".HIBYTE"><p>
1492 The function returns the high byte (that is, bits 8-15) of its argument.
1493 It works identical to the '>' operator.
1495 See: <tt><ref id=".LOBYTE" name=".LOBYTE"></tt>,
1496 <tt><ref id=".BANKBYTE" name=".BANKBYTE"></tt>
1499 <sect1><tt>.HIWORD</tt><label id=".HIWORD"><p>
1501 The function returns the high word (that is, bits 16-31) of its argument.
1503 See: <tt><ref id=".LOWORD" name=".LOWORD"></tt>
1506 <sect1><tt>.IDENT</tt><label id=".IDENT"><p>
1508 The function expects a string as its argument, and converts this argument
1509 into an identifier. If the string starts with the current <tt/<ref
1510 id=".LOCALCHAR" name=".LOCALCHAR">/, it will be converted into a cheap local
1511 identifier, otherwise it will be converted into a normal identifier.
1516 .macro makelabel arg1, arg2
1517 .ident (.concat (arg1, arg2)):
1520 makelabel "foo", "bar"
1522 .word foobar ; Valid label
1526 <sect1><tt>.LEFT</tt><label id=".LEFT"><p>
1528 Builtin function. Extracts the left part of a given token list.
1533 .LEFT (<int expr>, <token list>)
1536 The first integer expression gives the number of tokens to extract from
1537 the token list. The second argument is the token list itself. The token
1538 list may optionally be enclosed into curly braces. This allows the
1539 inclusion of tokens that would otherwise terminate the list (the closing
1540 right paren in the given case).
1544 To check in a macro if the given argument has a '#' as first token
1545 (immediate addressing mode), use something like this:
1550 .if (.match (.left (1, {arg}), #))
1552 ; ldax called with immediate operand
1560 See also the <tt><ref id=".MID" name=".MID"></tt> and <tt><ref id=".RIGHT"
1561 name=".RIGHT"></tt> builtin functions.
1564 <sect1><tt>.LOBYTE</tt><label id=".LOBYTE"><p>
1566 The function returns the low byte (that is, bits 0-7) of its argument.
1567 It works identical to the '<' operator.
1569 See: <tt><ref id=".HIBYTE" name=".HIBYTE"></tt>,
1570 <tt><ref id=".BANKBYTE" name=".BANKBYTE"></tt>
1573 <sect1><tt>.LOWORD</tt><label id=".LOWORD"><p>
1575 The function returns the low word (that is, bits 0-15) of its argument.
1577 See: <tt><ref id=".HIWORD" name=".HIWORD"></tt>
1580 <sect1><tt>.MATCH</tt><label id=".MATCH"><p>
1582 Builtin function. Matches two token lists against each other. This is
1583 most useful within macros, since macros are not stored as strings, but
1589 .MATCH(<token list #1>, <token list #2>)
1592 Both token list may contain arbitrary tokens with the exception of the
1593 terminator token (comma resp. right parenthesis) and
1600 The token lists may optionally be enclosed into curly braces. This allows
1601 the inclusion of tokens that would otherwise terminate the list (the closing
1602 right paren in the given case). Often a macro parameter is used for any of
1605 Please note that the function does only compare tokens, not token
1606 attributes. So any number is equal to any other number, regardless of the
1607 actual value. The same is true for strings. If you need to compare tokens
1608 <em/and/ token attributes, use the <tt><ref id=".XMATCH"
1609 name=".XMATCH"></tt> function.
1613 Assume the macro <tt/ASR/, that will shift right the accumulator by one,
1614 while honoring the sign bit. The builtin processor instructions will allow
1615 an optional "A" for accu addressing for instructions like <tt/ROL/ and
1616 <tt/ROR/. We will use the <tt><ref id=".MATCH" name=".MATCH"></tt> function
1617 to check for this and print and error for invalid calls.
1622 .if (.not .blank(arg)) .and (.not .match ({arg}, a))
1623 .error "Syntax error"
1626 cmp #$80 ; Bit 7 into carry
1627 lsr a ; Shift carry into bit 7
1632 The macro will only accept no arguments, or one argument that must be the
1633 reserved keyword "A".
1635 See: <tt><ref id=".XMATCH" name=".XMATCH"></tt>
1638 <sect1><tt>.MAX</tt><label id=".MAX"><p>
1640 Builtin function. The result is the larger of two values.
1645 .MAX (<value #1>, <value #2>)
1651 ; Reserve space for the larger of two data blocks
1652 savearea: .res .max (.sizeof (foo), .sizeof (bar))
1655 See: <tt><ref id=".MIN" name=".MIN"></tt>
1658 <sect1><tt>.MID</tt><label id=".MID"><p>
1660 Builtin function. Takes a starting index, a count and a token list as
1661 arguments. Will return part of the token list.
1666 .MID (<int expr>, <int expr>, <token list>)
1669 The first integer expression gives the starting token in the list (the first
1670 token has index 0). The second integer expression gives the number of tokens
1671 to extract from the token list. The third argument is the token list itself.
1672 The token list may optionally be enclosed into curly braces. This allows the
1673 inclusion of tokens that would otherwise terminate the list (the closing
1674 right paren in the given case).
1678 To check in a macro if the given argument has a '<tt/#/' as first token
1679 (immediate addressing mode), use something like this:
1684 .if (.match (.mid (0, 1, {arg}), #))
1686 ; ldax called with immediate operand
1694 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".RIGHT"
1695 name=".RIGHT"></tt> builtin functions.
1698 <sect1><tt>.MIN</tt><label id=".MIN"><p>
1700 Builtin function. The result is the smaller of two values.
1705 .MIN (<value #1>, <value #2>)
1711 ; Reserve space for some data, but 256 bytes maximum
1712 savearea: .res .min (.sizeof (foo), 256)
1715 See: <tt><ref id=".MAX" name=".MAX"></tt>
1718 <sect1><tt>.REF, .REFERENCED</tt><label id=".REFERENCED"><p>
1720 Builtin function. The function expects an identifier as argument in braces.
1721 The argument is evaluated, and the function yields "true" if the identifier
1722 is a symbol that has already been referenced somewhere in the source file up
1723 to the current position. Otherwise the function yields false. As an example,
1724 the <tt><ref id=".IFREF" name=".IFREF"></tt> statement may be replaced by
1730 See: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
1733 <sect1><tt>.RIGHT</tt><label id=".RIGHT"><p>
1735 Builtin function. Extracts the right part of a given token list.
1740 .RIGHT (<int expr>, <token list>)
1743 The first integer expression gives the number of tokens to extract from the
1744 token list. The second argument is the token list itself. The token list
1745 may optionally be enclosed into curly braces. This allows the inclusion of
1746 tokens that would otherwise terminate the list (the closing right paren in
1749 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".MID"
1750 name=".MID"></tt> builtin functions.
1753 <sect1><tt>.SIZEOF</tt><label id=".SIZEOF"><p>
1755 <tt/.SIZEOF/ is a pseudo function that returns the size of its argument. The
1756 argument can be a struct/union, a struct member, a procedure, or a label. In
1757 case of a procedure or label, its size is defined by the amount of data
1758 placed in the segment where the label is relative to. If a line of code
1759 switches segments (for example in a macro) data placed in other segments
1760 does not count for the size.
1762 Please note that a symbol or scope must exist, before it is used together with
1763 <tt/.SIZEOF/ (this may get relaxed later, but will always be true for scopes).
1764 A scope has preference over a symbol with the same name, so if the last part
1765 of a name represents both, a scope and a symbol, the scope is chosen over the
1768 After the following code:
1771 .struct Point ; Struct size = 4
1776 P: .tag Point ; Declare a point
1777 @P: .tag Point ; Declare another point
1789 .data ; Segment switch!!!
1795 <tag><tt/.sizeof(Point)/</tag>
1796 will have the value 4, because this is the size of struct <tt/Point/.
1798 <tag><tt/.sizeof(Point::xcoord)/</tag>
1799 will have the value 2, because this is the size of the member <tt/xcoord/
1800 in struct <tt/Point/.
1802 <tag><tt/.sizeof(P)/</tag>
1803 will have the value 4, this is the size of the data declared on the same
1804 source line as the label <tt/P/, which is in the same segment that <tt/P/
1807 <tag><tt/.sizeof(@P)/</tag>
1808 will have the value 4, see above. The example demonstrates that <tt/.SIZEOF/
1809 does also work for cheap local symbols.
1811 <tag><tt/.sizeof(Code)/</tag>
1812 will have the value 3, since this is amount of data emitted into the code
1813 segment, the segment that was active when <tt/Code/ was entered. Note that
1814 this value includes the amount of data emitted in child scopes (in this
1815 case <tt/Code::Inner/).
1817 <tag><tt/.sizeof(Code::Inner)/</tag>
1818 will have the value 1 as expected.
1820 <tag><tt/.sizeof(Data)/</tag>
1821 will have the value 0. Data is emitted within the scope <tt/Data/, but since
1822 the segment is switched after entry, this data is emitted into another
1827 <sect1><tt>.STRAT</tt><label id=".STRAT"><p>
1829 Builtin function. The function accepts a string and an index as
1830 arguments and returns the value of the character at the given position
1831 as an integer value. The index is zero based.
1837 ; Check if the argument string starts with '#'
1838 .if (.strat (Arg, 0) = '#')
1845 <sect1><tt>.SPRINTF</tt><label id=".SPRINTF"><p>
1847 Builtin function. It expects a format string as first argument. The number
1848 and type of the following arguments depend on the format string. The format
1849 string is similar to the one of the C <tt/printf/ function. Missing things
1850 are: Length modifiers, variable width.
1852 The result of the function is a string.
1859 ; Generate an identifier:
1860 .ident (.sprintf ("%s%03d", "label", num)):
1864 <sect1><tt>.STRING</tt><label id=".STRING"><p>
1866 Builtin function. The function accepts an argument in braces and converts
1867 this argument into a string constant. The argument may be an identifier, or
1868 a constant numeric value.
1870 Since you can use a string in the first place, the use of the function may
1871 not be obvious. However, it is useful in macros, or more complex setups.
1876 ; Emulate other assemblers:
1878 .segment .string(name)
1883 <sect1><tt>.STRLEN</tt><label id=".STRLEN"><p>
1885 Builtin function. The function accepts a string argument in braces and
1886 evaluates to the length of the string.
1890 The following macro encodes a string as a pascal style string with
1891 a leading length byte.
1895 .byte .strlen(Arg), Arg
1900 <sect1><tt>.TCOUNT</tt><label id=".TCOUNT"><p>
1902 Builtin function. The function accepts a token list in braces. The function
1903 result is the number of tokens given as argument. The token list may
1904 optionally be enclosed into curly braces which are not considered part of
1905 the list and not counted. Enclosement in curly braces allows the inclusion
1906 of tokens that would otherwise terminate the list (the closing right paren
1911 The <tt/ldax/ macro accepts the '#' token to denote immediate addressing (as
1912 with the normal 6502 instructions). To translate it into two separate 8 bit
1913 load instructions, the '#' token has to get stripped from the argument:
1917 .if (.match (.mid (0, 1, {arg}), #))
1918 ; ldax called with immediate operand
1919 lda #<(.right (.tcount ({arg})-1, {arg}))
1920 ldx #>(.right (.tcount ({arg})-1, {arg}))
1928 <sect1><tt>.XMATCH</tt><label id=".XMATCH"><p>
1930 Builtin function. Matches two token lists against each other. This is
1931 most useful within macros, since macros are not stored as strings, but
1937 .XMATCH(<token list #1>, <token list #2>)
1940 Both token list may contain arbitrary tokens with the exception of the
1941 terminator token (comma resp. right parenthesis) and
1948 The token lists may optionally be enclosed into curly braces. This allows
1949 the inclusion of tokens that would otherwise terminate the list (the closing
1950 right paren in the given case). Often a macro parameter is used for any of
1953 The function compares tokens <em/and/ token values. If you need a function
1954 that just compares the type of tokens, have a look at the <tt><ref
1955 id=".MATCH" name=".MATCH"></tt> function.
1957 See: <tt><ref id=".MATCH" name=".MATCH"></tt>
1961 <sect>Control commands<label id="control-commands"><p>
1963 Here's a list of all control commands and a description, what they do:
1966 <sect1><tt>.A16</tt><label id=".A16"><p>
1968 Valid only in 65816 mode. Switch the accumulator to 16 bit.
1970 Note: This command will not emit any code, it will tell the assembler to
1971 create 16 bit operands for immediate accumulator addressing mode.
1973 See also: <tt><ref id=".SMART" name=".SMART"></tt>
1976 <sect1><tt>.A8</tt><label id=".A8"><p>
1978 Valid only in 65816 mode. Switch the accumulator to 8 bit.
1980 Note: This command will not emit any code, it will tell the assembler to
1981 create 8 bit operands for immediate accu addressing mode.
1983 See also: <tt><ref id=".SMART" name=".SMART"></tt>
1986 <sect1><tt>.ADDR</tt><label id=".ADDR"><p>
1988 Define word sized data. In 6502 mode, this is an alias for <tt/.WORD/ and
1989 may be used for better readability if the data words are address values. In
1990 65816 mode, the address is forced to be 16 bit wide to fit into the current
1991 segment. See also <tt><ref id=".FARADDR" name=".FARADDR"></tt>. The command
1992 must be followed by a sequence of (not necessarily constant) expressions.
1997 .addr $0D00, $AF13, _Clear
2000 See: <tt><ref id=".FARADDR" name=".FARADDR"></tt>, <tt><ref id=".WORD"
2004 <sect1><tt>.ALIGN</tt><label id=".ALIGN"><p>
2006 Align data to a given boundary. The command expects a constant integer
2007 argument in the range 1 ... 65536, plus an optional second argument
2008 in byte range. If there is a second argument, it is used as fill value,
2009 otherwise the value defined in the linker configuration file is used
2010 (the default for this value is zero).
2012 <tt/.ALIGN/ will insert fill bytes, and the number of fill bytes depend of
2013 the final address of the segment. <tt/.ALIGN/ cannot insert a variable
2014 number of bytes, since that would break address calculations within the
2015 module. So each <tt/.ALIGN/ expects the segment to be aligned to a multiple
2016 of the alignment, because that allows the number of fill bytes to be
2017 calculated in advance by the assembler. You are therefore required to
2018 specify a matching alignment for the segment in the linker config. The
2019 linker will output a warning if the alignment of the segment is less than
2020 what is necessary to have a correct alignment in the object file.
2028 Some unexpected behaviour might occur if there are multiple <tt/.ALIGN/
2029 commands with different arguments. To allow the assembler to calculate the
2030 number of fill bytes in advance, the alignment of the segment must be a
2031 multiple of each of the alignment factors. This may result in unexpectedly
2032 large alignments for the segment within the module.
2043 For the assembler to be able to align correctly, the segment must be aligned
2044 to the least common multiple of 15 and 18 which is 90. The assembler will
2045 calculate this automatically and will mark the segment with this value.
2047 Unfortunately, the combined alignment may get rather large without the user
2048 knowing about it, wasting space in the final executable. If we add another
2049 alignment to the example above
2060 the assembler will force a segment alignment to the least common multiple of
2061 15, 18 and 251 - which is 22590. To protect the user against errors, the
2062 assembler will issue a warning when the combined alignment exceeds 256. The
2063 command line option <tt><ref id="option--large-alignment"
2064 name="--large-alignment"></tt> will disable this warning.
2066 Please note that with alignments that are a power of two (which were the
2067 only alignments possible in older versions of the assembler), the problem is
2068 less severe, because the least common multiple of powers to the same base is
2069 always the larger one.
2073 <sect1><tt>.ASCIIZ</tt><label id=".ASCIIZ"><p>
2075 Define a string with a trailing zero.
2080 Msg: .asciiz "Hello world"
2083 This will put the string "Hello world" followed by a binary zero into
2084 the current segment. There may be more strings separated by commas, but
2085 the binary zero is only appended once (after the last one).
2088 <sect1><tt>.ASSERT</tt><label id=".ASSERT"><p>
2090 Add an assertion. The command is followed by an expression, an action
2091 specifier, and an optional message that is output in case the assertion
2092 fails. If no message was given, the string "Assertion failed" is used. The
2093 action specifier may be one of <tt/warning/, <tt/error/, <tt/ldwarning/ or
2094 <tt/lderror/. In the former two cases, the assertion is evaluated by the
2095 assembler if possible, and in any case, it's also passed to the linker in
2096 the object file (if one is generated). The linker will then evaluate the
2097 expression when segment placement has been done.
2102 .assert * = $8000, error, "Code not at $8000"
2105 The example assertion will check that the current location is at $8000,
2106 when the output file is written, and abort with an error if this is not
2107 the case. More complex expressions are possible. The action specifier
2108 <tt/warning/ outputs a warning, while the <tt/error/ specifier outputs
2109 an error message. In the latter case, generation of the output file is
2110 suppressed in both the assembler and linker.
2113 <sect1><tt>.AUTOIMPORT</tt><label id=".AUTOIMPORT"><p>
2115 Is followed by a plus or a minus character. When switched on (using a
2116 +), undefined symbols are automatically marked as import instead of
2117 giving errors. When switched off (which is the default so this does not
2118 make much sense), this does not happen and an error message is
2119 displayed. The state of the autoimport flag is evaluated when the
2120 complete source was translated, before outputting actual code, so it is
2121 <em/not/ possible to switch this feature on or off for separate sections
2122 of code. The last setting is used for all symbols.
2124 You should probably not use this switch because it delays error
2125 messages about undefined symbols until the link stage. The cc65
2126 compiler (which is supposed to produce correct assembler code in all
2127 circumstances, something which is not true for most assembler
2128 programmers) will insert this command to avoid importing each and every
2129 routine from the runtime library.
2134 .autoimport + ; Switch on auto import
2137 <sect1><tt>.BANKBYTES</tt><label id=".BANKBYTES"><p>
2139 Define byte sized data by extracting only the bank byte (that is, bits 16-23) from
2140 each expression. This is equivalent to <tt><ref id=".BYTE" name=".BYTE"></tt> with
2141 the operator '^' prepended to each expression in its list.
2146 .define MyTable TableItem0, TableItem1, TableItem2, TableItem3
2148 TableLookupLo: .lobytes MyTable
2149 TableLookupHi: .hibytes MyTable
2150 TableLookupBank: .bankbytes MyTable
2153 which is equivalent to
2156 TableLookupLo: .byte <TableItem0, <TableItem1, <TableItem2, <TableItem3
2157 TableLookupHi: .byte >TableItem0, >TableItem1, >TableItem2, >TableItem3
2158 TableLookupBank: .byte ^TableItem0, ^TableItem1, ^TableItem2, ^TableItem3
2161 See also: <tt><ref id=".BYTE" name=".BYTE"></tt>,
2162 <tt><ref id=".HIBYTES" name=".HIBYTES"></tt>,
2163 <tt><ref id=".LOBYTES" name=".LOBYTES"></tt>
2166 <sect1><tt>.BSS</tt><label id=".BSS"><p>
2168 Switch to the BSS segment. The name of the BSS segment is always "BSS",
2169 so this is a shortcut for
2175 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
2178 <sect1><tt>.BYT, .BYTE</tt><label id=".BYTE"><p>
2180 Define byte sized data. Must be followed by a sequence of (byte ranged)
2181 expressions or strings.
2187 .byt "world", $0D, $00
2191 <sect1><tt>.CASE</tt><label id=".CASE"><p>
2193 Switch on or off case sensitivity on identifiers. The default is off
2194 (that is, identifiers are case sensitive), but may be changed by the
2195 -i switch on the command line.
2196 The command must be followed by a '+' or '-' character to switch the
2197 option on or off respectively.
2202 .case - ; Identifiers are not case sensitive
2206 <sect1><tt>.CHARMAP</tt><label id=".CHARMAP"><p>
2208 Apply a custom mapping for characters. The command is followed by two
2209 numbers. The first one is the index of the source character (range 0..255);
2210 the second one is the mapping (range 0..255). The mapping applies to all
2211 character and string constants <em/when/ they generate output; and, overrides
2212 a mapping table specified with the <tt><ref id="option-t" name="-t"></tt>
2213 command line switch.
2217 .charmap $41, $61 ; Map 'A' to 'a'
2221 <sect1><tt>.CODE</tt><label id=".CODE"><p>
2223 Switch to the CODE segment. The name of the CODE segment is always
2224 "CODE", so this is a shortcut for
2230 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
2233 <sect1><tt>.CONDES</tt><label id=".CONDES"><p>
2235 Export a symbol and mark it in a special way. The linker is able to build
2236 tables of all such symbols. This may be used to automatically create a list
2237 of functions needed to initialize linked library modules.
2239 Note: The linker has a feature to build a table of marked routines, but it
2240 is your code that must call these routines, so just declaring a symbol with
2241 <tt/.CONDES/ does nothing by itself.
2243 All symbols are exported as an absolute (16 bit) symbol. You don't need to
2244 use an additional <tt><ref id=".EXPORT" name=".EXPORT"></tt> statement, this
2245 is implied by <tt/.CONDES/.
2247 <tt/.CONDES/ is followed by the type, which may be <tt/constructor/,
2248 <tt/destructor/ or a numeric value between 0 and 6 (where 0 is the same as
2249 specifying <tt/constructor/ and 1 is equal to specifying <tt/destructor/).
2250 The <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
2251 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
2252 name=".INTERRUPTOR"></tt> commands are actually shortcuts for <tt/.CONDES/
2253 with a type of <tt/constructor/ resp. <tt/destructor/ or <tt/interruptor/.
2255 After the type, an optional priority may be specified. Higher numeric values
2256 mean higher priority. If no priority is given, the default priority of 7 is
2257 used. Be careful when assigning priorities to your own module constructors
2258 so they won't interfere with the ones in the cc65 library.
2263 .condes ModuleInit, constructor
2264 .condes ModInit, 0, 16
2267 See the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
2268 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
2269 name=".INTERRUPTOR"></tt> commands and the separate section <ref id="condes"
2270 name="Module constructors/destructors"> explaining the feature in more
2274 <sect1><tt>.CONSTRUCTOR</tt><label id=".CONSTRUCTOR"><p>
2276 Export a symbol and mark it as a module constructor. This may be used
2277 together with the linker to build a table of constructor subroutines that
2278 are called by the startup code.
2280 Note: The linker has a feature to build a table of marked routines, but it
2281 is your code that must call these routines, so just declaring a symbol as
2282 constructor does nothing by itself.
2284 A constructor is always exported as an absolute (16 bit) symbol. You don't
2285 need to use an additional <tt/.export/ statement, this is implied by
2286 <tt/.constructor/. It may have an optional priority that is separated by a
2287 comma. Higher numeric values mean a higher priority. If no priority is
2288 given, the default priority of 7 is used. Be careful when assigning
2289 priorities to your own module constructors so they won't interfere with the
2290 ones in the cc65 library.
2295 .constructor ModuleInit
2296 .constructor ModInit, 16
2299 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
2300 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands and the separate section
2301 <ref id="condes" name="Module constructors/destructors"> explaining the
2302 feature in more detail.
2305 <sect1><tt>.DATA</tt><label id=".DATA"><p>
2307 Switch to the DATA segment. The name of the DATA segment is always
2308 "DATA", so this is a shortcut for
2314 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
2317 <sect1><tt>.DBYT</tt><label id=".DBYT"><p>
2319 Define word sized data with the hi and lo bytes swapped (use <tt/.WORD/ to
2320 create word sized data in native 65XX format). Must be followed by a
2321 sequence of (word ranged) expressions.
2329 This will emit the bytes
2335 into the current segment in that order.
2338 <sect1><tt>.DEBUGINFO</tt><label id=".DEBUGINFO"><p>
2340 Switch on or off debug info generation. The default is off (that is,
2341 the object file will not contain debug infos), but may be changed by the
2342 -g switch on the command line.
2343 The command must be followed by a '+' or '-' character to switch the
2344 option on or off respectively.
2349 .debuginfo + ; Generate debug info
2353 <sect1><tt>.DEFINE</tt><label id=".DEFINE"><p>
2355 Start a define style macro definition. The command is followed by an
2356 identifier (the macro name) and optionally by a list of formal arguments
2359 Please note that <tt/.DEFINE/ shares most disadvantages with its C
2360 counterpart, so the general advice is, <bf/NOT/ do use <tt/.DEFINE/ if you
2363 See also the <tt><ref id=".UNDEFINE" name=".UNDEFINE"></tt> command and
2364 section <ref id="macros" name="Macros">.
2367 <sect1><tt>.DELMAC, .DELMACRO</tt><label id=".DELMACRO"><p>
2369 Delete a classic macro (defined with <tt><ref id=".MACRO"
2370 name=".MACRO"></tt>) . The command is followed by the name of an
2371 existing macro. Its definition will be deleted together with the name.
2372 If necessary, another macro with this name may be defined later.
2374 See: <tt><ref id=".ENDMACRO" name=".ENDMACRO"></tt>,
2375 <tt><ref id=".EXITMACRO" name=".EXITMACRO"></tt>,
2376 <tt><ref id=".MACRO" name=".MACRO"></tt>
2378 See also section <ref id="macros" name="Macros">.
2381 <sect1><tt>.DEF, .DEFINED</tt><label id=".DEFINED"><p>
2383 Builtin function. The function expects an identifier as argument in braces.
2384 The argument is evaluated, and the function yields "true" if the identifier
2385 is a symbol that is already defined somewhere in the source file up to the
2386 current position. Otherwise the function yields false. As an example, the
2387 <tt><ref id=".IFDEF" name=".IFDEF"></tt> statement may be replaced by
2394 <sect1><tt>.DEFINEDMACRO</tt><label id=".DEFINEDMACRO"><p>
2396 Builtin function. The function expects an identifier as argument in braces.
2397 The argument is evaluated, and the function yields "true" if the identifier
2398 has already been defined as the name of a macro. Otherwise the function yields
2407 .if .definedmacro(add)
2416 <sect1><tt>.DESTRUCTOR</tt><label id=".DESTRUCTOR"><p>
2418 Export a symbol and mark it as a module destructor. This may be used
2419 together with the linker to build a table of destructor subroutines that
2420 are called by the startup code.
2422 Note: The linker has a feature to build a table of marked routines, but it
2423 is your code that must call these routines, so just declaring a symbol as
2424 constructor does nothing by itself.
2426 A destructor is always exported as an absolute (16 bit) symbol. You don't
2427 need to use an additional <tt/.export/ statement, this is implied by
2428 <tt/.destructor/. It may have an optional priority that is separated by a
2429 comma. Higher numerical values mean a higher priority. If no priority is
2430 given, the default priority of 7 is used. Be careful when assigning
2431 priorities to your own module destructors so they won't interfere with the
2432 ones in the cc65 library.
2437 .destructor ModuleDone
2438 .destructor ModDone, 16
2441 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
2442 id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> commands and the separate
2443 section <ref id="condes" name="Module constructors/destructors"> explaining
2444 the feature in more detail.
2447 <sect1><tt>.DWORD</tt><label id=".DWORD"><p>
2449 Define dword sized data (4 bytes) Must be followed by a sequence of
2455 .dword $12344512, $12FA489
2459 <sect1><tt>.ELSE</tt><label id=".ELSE"><p>
2461 Conditional assembly: Reverse the current condition.
2464 <sect1><tt>.ELSEIF</tt><label id=".ELSEIF"><p>
2466 Conditional assembly: Reverse current condition and test a new one.
2469 <sect1><tt>.END</tt><label id=".END"><p>
2471 Forced end of assembly. Assembly stops at this point, even if the command
2472 is read from an include file.
2475 <sect1><tt>.ENDENUM</tt><label id=".ENDENUM"><p>
2477 End a <tt><ref id=".ENUM" name=".ENUM"></tt> declaration.
2480 <sect1><tt>.ENDIF</tt><label id=".ENDIF"><p>
2482 Conditional assembly: Close a <tt><ref id=".IF" name=".IF..."></tt> or
2483 <tt><ref id=".ELSE" name=".ELSE"></tt> branch.
2486 <sect1><tt>.ENDMAC, .ENDMACRO</tt><label id=".ENDMACRO"><p>
2488 Marks the end of a macro definition.
2490 See: <tt><ref id=".DELMACRO" name=".DELMACRO"></tt>,
2491 <tt><ref id=".EXITMACRO" name=".EXITMACRO"></tt>,
2492 <tt><ref id=".MACRO" name=".MACRO"></tt>
2494 See also section <ref id="macros" name="Macros">.
2497 <sect1><tt>.ENDPROC</tt><label id=".ENDPROC"><p>
2499 End of local lexical level (see <tt><ref id=".PROC" name=".PROC"></tt>).
2502 <sect1><tt>.ENDREP, .ENDREPEAT</tt><label id=".ENDREPEAT"><p>
2504 End a <tt><ref id=".REPEAT" name=".REPEAT"></tt> block.
2507 <sect1><tt>.ENDSCOPE</tt><label id=".ENDSCOPE"><p>
2509 End of local lexical level (see <tt/<ref id=".SCOPE" name=".SCOPE">/).
2512 <sect1><tt>.ENDSTRUCT</tt><label id=".ENDSTRUCT"><p>
2514 Ends a struct definition. See the <tt/<ref id=".STRUCT" name=".STRUCT">/
2515 command and the separate section named <ref id="structs" name=""Structs
2519 <sect1><tt>.ENDUNION</tt><label id=".ENDUNION"><p>
2521 Ends a union definition. See the <tt/<ref id=".UNION" name=".UNION">/
2522 command and the separate section named <ref id="structs" name=""Structs
2526 <sect1><tt>.ENUM</tt><label id=".ENUM"><p>
2528 Start an enumeration. This directive is very similar to the C <tt/enum/
2529 keyword. If a name is given, a new scope is created for the enumeration,
2530 otherwise the enumeration members are placed in the enclosing scope.
2532 In the enumeration body, symbols are declared. The first symbol has a value
2533 of zero, and each following symbol will get the value of the preceding plus
2534 one. This behaviour may be overridden by an explicit assignment. Two symbols
2535 may have the same value.
2547 Above example will create a new scope named <tt/errorcodes/ with three
2548 symbols in it that get the values 0, 1 and 2 respectively. Another way
2549 to write this would have been:
2559 Please note that explicit scoping must be used to access the identifiers:
2562 .word errorcodes::no_error
2565 A more complex example:
2574 EWOULDBLOCK = EAGAIN
2578 In this example, the enumeration does not have a name, which means that the
2579 members will be visible in the enclosing scope and can be used in this scope
2580 without explicit scoping. The first member (<tt/EUNKNOWN/) has the value -1.
2581 The value for the following members is incremented by one, so <tt/EOK/ would
2582 be zero and so on. <tt/EWOULDBLOCK/ is an alias for <tt/EGAIN/, so it has an
2583 override for the value using an already defined symbol.
2586 <sect1><tt>.ERROR</tt><label id=".ERROR"><p>
2588 Force an assembly error. The assembler will output an error message
2589 preceded by "User error". Assembly is continued but no object file will
2592 This command may be used to check for initial conditions that must be
2593 set before assembling a source file.
2603 .error "Must define foo or bar!"
2607 See also: <tt><ref id=".FATAL" name=".FATAL"></tt>,
2608 <tt><ref id=".OUT" name=".OUT"></tt>,
2609 <tt><ref id=".WARNING" name=".WARNING"></tt>
2612 <sect1><tt>.EXITMAC, .EXITMACRO</tt><label id=".EXITMACRO"><p>
2614 Abort a macro expansion immediately. This command is often useful in
2617 See: <tt><ref id=".DELMACRO" name=".DELMACRO"></tt>,
2618 <tt><ref id=".ENDMACRO" name=".ENDMACRO"></tt>,
2619 <tt><ref id=".MACRO" name=".MACRO"></tt>
2621 See also section <ref id="macros" name="Macros">.
2624 <sect1><tt>.EXPORT</tt><label id=".EXPORT"><p>
2626 Make symbols accessible from other modules. Must be followed by a comma
2627 separated list of symbols to export, with each one optionally followed by an
2628 address specification and (also optional) an assignment. Using an additional
2629 assignment in the export statement allows to define and export a symbol in
2630 one statement. The default is to export the symbol with the address size it
2631 actually has. The assembler will issue a warning, if the symbol is exported
2632 with an address size smaller than the actual address size.
2639 .export foobar: far = foo * bar
2640 .export baz := foobar, zap: far = baz - bar
2643 As with constant definitions, using <tt/:=/ instead of <tt/=/ marks the
2646 See: <tt><ref id=".EXPORTZP" name=".EXPORTZP"></tt>
2649 <sect1><tt>.EXPORTZP</tt><label id=".EXPORTZP"><p>
2651 Make symbols accessible from other modules. Must be followed by a comma
2652 separated list of symbols to export. The exported symbols are explicitly
2653 marked as zero page symbols. An assignment may be included in the
2654 <tt/.EXPORTZP/ statement. This allows to define and export a symbol in one
2661 .exportzp baz := $02
2664 See: <tt><ref id=".EXPORT" name=".EXPORT"></tt>
2667 <sect1><tt>.FARADDR</tt><label id=".FARADDR"><p>
2669 Define far (24 bit) address data. The command must be followed by a
2670 sequence of (not necessarily constant) expressions.
2675 .faraddr DrawCircle, DrawRectangle, DrawHexagon
2678 See: <tt><ref id=".ADDR" name=".ADDR"></tt>
2681 <sect1><tt>.FATAL</tt><label id=".FATAL"><p>
2683 Force an assembly error and terminate assembly. The assembler will output an
2684 error message preceded by "User error" and will terminate assembly
2687 This command may be used to check for initial conditions that must be
2688 set before assembling a source file.
2698 .fatal "Must define foo or bar!"
2702 See also: <tt><ref id=".ERROR" name=".ERROR"></tt>,
2703 <tt><ref id=".OUT" name=".OUT"></tt>,
2704 <tt><ref id=".WARNING" name=".WARNING"></tt>
2707 <sect1><tt>.FEATURE</tt><label id=".FEATURE"><p>
2709 This directive may be used to enable one or more compatibility features
2710 of the assembler. While the use of <tt/.FEATURE/ should be avoided when
2711 possible, it may be useful when porting sources written for other
2712 assemblers. There is no way to switch a feature off, once you have
2713 enabled it, so using
2719 will enable the feature until end of assembly is reached.
2721 The following features are available:
2725 <tag><tt>addrsize</tt><label id="addrsize"></tag>
2727 Enables the .ADDRSIZE pseudo function. This function is experimental and not enabled by default.
2729 See also: <tt><ref id=".ADDRSIZE" name=".ADDRSIZE"></tt>
2731 <tag><tt>at_in_identifiers</tt><label id="at_in_identifiers"></tag>
2733 Accept the at character (`@') as a valid character in identifiers. The
2734 at character is not allowed to start an identifier, even with this
2737 <tag><tt>bracket_as_indirect</tt><label id="bracket_as_indirect"></tag>
2739 Use <tt>[]</tt> instead of <tt>()</tt> for the indirect addressing modes.
2749 <em/Note:/ This should not be used in 65186 mode because it conflicts with
2750 the 65816 instruction syntax for far addressing. See the section covering
2751 <tt/<ref id="address-sizes" name="address sizes">/ for more information.
2753 <tag><tt>c_comments</tt><label id="c_comments"></tag>
2755 Allow C like comments using <tt>/*</tt> and <tt>*/</tt> as left and right
2756 comment terminators. Note that C comments may not be nested. There's also a
2757 pitfall when using C like comments: All statements must be terminated by
2758 "end-of-line". Using C like comments, it is possible to hide the newline,
2759 which results in error messages. See the following non working example:
2762 lda #$00 /* This comment hides the newline
2766 <tag><tt>dollar_in_identifiers</tt><label id="dollar_in_identifiers"></tag>
2768 Accept the dollar sign (`$') as a valid character in identifiers. The
2769 dollar character is not allowed to start an identifier, even with this
2772 <tag><tt>dollar_is_pc</tt><label id="dollar_is_pc"></tag>
2774 The dollar sign may be used as an alias for the star (`*'), which
2775 gives the value of the current PC in expressions.
2776 Note: Assignment to the pseudo variable is not allowed.
2778 <tag><tt>force_range</tt><label id="force_range"></tag>
2780 Force expressions into their valid range for immediate addressing and
2781 storage operators like <tt><ref id=".BYTE" name=".BYTE"></tt> and
2782 <tt><ref id=".WORD" name=".WORD"></tt>. Be very careful with this one,
2783 since it will completely disable error checks.
2785 <tag><tt>labels_without_colons</tt><label id="labels_without_colons"></tag>
2787 Allow labels without a trailing colon. These labels are only accepted,
2788 if they start at the beginning of a line (no leading white space).
2790 <tag><tt>leading_dot_in_identifiers</tt><label id="leading_dot_in_identifiers"></tag>
2792 Accept the dot (`.') as the first character of an identifier. This may be
2793 used for example to create macro names that start with a dot emulating
2794 control directives of other assemblers. Note however, that none of the
2795 reserved keywords built into the assembler, that starts with a dot, may be
2796 overridden. When using this feature, you may also get into trouble if
2797 later versions of the assembler define new keywords starting with a dot.
2799 <tag><tt>loose_char_term</tt><label id="loose_char_term"></tag>
2801 Accept single quotes as well as double quotes as terminators for char
2804 <tag><tt>loose_string_term</tt><label id="loose_string_term"></tag>
2806 Accept single quotes as well as double quotes as terminators for string
2809 <tag><tt>missing_char_term</tt><label id="missing_char_term"></tag>
2811 Accept single quoted character constants where the terminating quote is
2816 <em/Note:/ This does not work in conjunction with <tt/.FEATURE
2817 loose_string_term/, since in this case the input would be ambiguous.
2819 <tag><tt>org_per_seg</tt><label id="org_per_seg"></tag>
2821 This feature makes relocatable/absolute mode local to the current segment.
2822 Using <tt><ref id=".ORG" name=".ORG"></tt> when <tt/org_per_seg/ is in
2823 effect will only enable absolute mode for the current segment. Dito for
2824 <tt><ref id=".RELOC" name=".RELOC"></tt>.
2826 <tag><tt>pc_assignment</tt><label id="pc_assignment"></tag>
2828 Allow assignments to the PC symbol (`*' or `$' if <tt/dollar_is_pc/
2829 is enabled). Such an assignment is handled identical to the <tt><ref
2830 id=".ORG" name=".ORG"></tt> command (which is usually not needed, so just
2831 removing the lines with the assignments may also be an option when porting
2832 code written for older assemblers).
2834 <tag><tt>ubiquitous_idents</tt><label id="ubiquitous_idents"></tag>
2836 Allow the use of instructions names as names for macros and symbols. This
2837 makes it possible to "overload" instructions by defining a macro with the
2838 same name. This does also make it possible to introduce hard to find errors
2839 in your code, so be careful!
2841 <tag><tt>underline_in_numbers</tt><label id="underline_in_numbers"></tag>
2843 Allow underlines within numeric constants. These may be used for grouping
2844 the digits of numbers for easier reading.
2847 .feature underline_in_numbers
2848 .word %1100001110100101
2849 .word %1100_0011_1010_0101 ; Identical but easier to read
2854 It is also possible to specify features on the command line using the
2855 <tt><ref id="option--feature" name="--feature"></tt> command line option.
2856 This is useful when translating sources written for older assemblers, when
2857 you don't want to change the source code.
2859 As an example, to translate sources written for Andre Fachats xa65
2860 assembler, the features
2863 labels_without_colons, pc_assignment, loose_char_term
2866 may be helpful. They do not make ca65 completely compatible, so you may not
2867 be able to translate the sources without changes, even when enabling these
2868 features. However, I have found several sources that translate without
2869 problems when enabling these features on the command line.
2872 <sect1><tt>.FILEOPT, .FOPT</tt><label id=".FOPT"><p>
2874 Insert an option string into the object file. There are two forms of
2875 this command, one specifies the option by a keyword, the second
2876 specifies it as a number. Since usage of the second one needs knowledge
2877 of the internal encoding, its use is not recommended and I will only
2878 describe the first form here.
2880 The command is followed by one of the keywords
2888 a comma and a string. The option is written into the object file
2889 together with the string value. This is currently unidirectional and
2890 there is no way to actually use these options once they are in the
2896 .fileopt comment, "Code stolen from my brother"
2897 .fileopt compiler, "BASIC 2.0"
2898 .fopt author, "J. R. User"
2902 <sect1><tt>.FORCEIMPORT</tt><label id=".FORCEIMPORT"><p>
2904 Import an absolute symbol from another module. The command is followed by a
2905 comma separated list of symbols to import. The command is similar to <tt>
2906 <ref id=".IMPORT" name=".IMPORT"></tt>, but the import reference is always
2907 written to the generated object file, even if the symbol is never referenced
2908 (<tt><ref id=".IMPORT" name=".IMPORT"></tt> will not generate import
2909 references for unused symbols).
2914 .forceimport needthisone, needthistoo
2917 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
2920 <sect1><tt>.GLOBAL</tt><label id=".GLOBAL"><p>
2922 Declare symbols as global. Must be followed by a comma separated list of
2923 symbols to declare. Symbols from the list, that are defined somewhere in the
2924 source, are exported, all others are imported. Additional <tt><ref
2925 id=".IMPORT" name=".IMPORT"></tt> or <tt><ref id=".EXPORT"
2926 name=".EXPORT"></tt> commands for the same symbol are allowed.
2935 <sect1><tt>.GLOBALZP</tt><label id=".GLOBALZP"><p>
2937 Declare symbols as global. Must be followed by a comma separated list of
2938 symbols to declare. Symbols from the list, that are defined somewhere in the
2939 source, are exported, all others are imported. Additional <tt><ref
2940 id=".IMPORTZP" name=".IMPORTZP"></tt> or <tt><ref id=".EXPORTZP"
2941 name=".EXPORTZP"></tt> commands for the same symbol are allowed. The symbols
2942 in the list are explicitly marked as zero page symbols.
2950 <sect1><tt>.HIBYTES</tt><label id=".HIBYTES"><p>
2952 Define byte sized data by extracting only the high byte (that is, bits 8-15) from
2953 each expression. This is equivalent to <tt><ref id=".BYTE" name=".BYTE"></tt> with
2954 the operator '>' prepended to each expression in its list.
2959 .lobytes $1234, $2345, $3456, $4567
2960 .hibytes $fedc, $edcb, $dcba, $cba9
2963 which is equivalent to
2966 .byte $34, $45, $56, $67
2967 .byte $fe, $ed, $dc, $cb
2973 .define MyTable TableItem0, TableItem1, TableItem2, TableItem3
2975 TableLookupLo: .lobytes MyTable
2976 TableLookupHi: .hibytes MyTable
2979 which is equivalent to
2982 TableLookupLo: .byte <TableItem0, <TableItem1, <TableItem2, <TableItem3
2983 TableLookupHi: .byte >TableItem0, >TableItem1, >TableItem2, >TableItem3
2986 See also: <tt><ref id=".BYTE" name=".BYTE"></tt>,
2987 <tt><ref id=".LOBYTES" name=".LOBYTES"></tt>,
2988 <tt><ref id=".BANKBYTES" name=".BANKBYTES"></tt>
2991 <sect1><tt>.I16</tt><label id=".I16"><p>
2993 Valid only in 65816 mode. Switch the index registers to 16 bit.
2995 Note: This command will not emit any code, it will tell the assembler to
2996 create 16 bit operands for immediate operands.
2998 See also the <tt><ref id=".I8" name=".I8"></tt> and <tt><ref id=".SMART"
2999 name=".SMART"></tt> commands.
3002 <sect1><tt>.I8</tt><label id=".I8"><p>
3004 Valid only in 65816 mode. Switch the index registers to 8 bit.
3006 Note: This command will not emit any code, it will tell the assembler to
3007 create 8 bit operands for immediate operands.
3009 See also the <tt><ref id=".I16" name=".I16"></tt> and <tt><ref id=".SMART"
3010 name=".SMART"></tt> commands.
3013 <sect1><tt>.IF</tt><label id=".IF"><p>
3015 Conditional assembly: Evaluate an expression and switch assembler output
3016 on or off depending on the expression. The expression must be a constant
3017 expression, that is, all operands must be defined.
3019 A expression value of zero evaluates to FALSE, any other value evaluates
3023 <sect1><tt>.IFBLANK</tt><label id=".IFBLANK"><p>
3025 Conditional assembly: Check if there are any remaining tokens in this line,
3026 and evaluate to FALSE if this is the case, and to TRUE otherwise. If the
3027 condition is not true, further lines are not assembled until an <tt><ref
3028 id=".ELSE" name=".ELSE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
3029 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
3031 This command is often used to check if a macro parameter was given. Since an
3032 empty macro parameter will evaluate to nothing, the condition will evaluate
3033 to TRUE if an empty parameter was given.
3047 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
3050 <sect1><tt>.IFCONST</tt><label id=".IFCONST"><p>
3052 Conditional assembly: Evaluate an expression and switch assembler output
3053 on or off depending on the constness of the expression.
3055 A const expression evaluates to to TRUE, a non const expression (one
3056 containing an imported or currently undefined symbol) evaluates to
3059 See also: <tt><ref id=".CONST" name=".CONST"></tt>
3062 <sect1><tt>.IFDEF</tt><label id=".IFDEF"><p>
3064 Conditional assembly: Check if a symbol is defined. Must be followed by
3065 a symbol name. The condition is true if the the given symbol is already
3066 defined, and false otherwise.
3068 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
3071 <sect1><tt>.IFNBLANK</tt><label id=".IFNBLANK"><p>
3073 Conditional assembly: Check if there are any remaining tokens in this line,
3074 and evaluate to TRUE if this is the case, and to FALSE otherwise. If the
3075 condition is not true, further lines are not assembled until an <tt><ref
3076 id=".ELSE" name=".ELSE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
3077 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
3079 This command is often used to check if a macro parameter was given.
3080 Since an empty macro parameter will evaluate to nothing, the condition
3081 will evaluate to FALSE if an empty parameter was given.
3094 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
3097 <sect1><tt>.IFNDEF</tt><label id=".IFNDEF"><p>
3099 Conditional assembly: Check if a symbol is defined. Must be followed by
3100 a symbol name. The condition is true if the the given symbol is not
3101 defined, and false otherwise.
3103 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
3106 <sect1><tt>.IFNREF</tt><label id=".IFNREF"><p>
3108 Conditional assembly: Check if a symbol is referenced. Must be followed
3109 by a symbol name. The condition is true if if the the given symbol was
3110 not referenced before, and false otherwise.
3112 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
3115 <sect1><tt>.IFP02</tt><label id=".IFP02"><p>
3117 Conditional assembly: Check if the assembler is currently in 6502 mode
3118 (see <tt><ref id=".P02" name=".P02"></tt> command).
3121 <sect1><tt>.IFP4510</tt><label id=".IFP4510"><p>
3123 Conditional assembly: Check if the assembler is currently in 4510 mode
3124 (see <tt><ref id=".P4510" name=".P4510"></tt> command).
3127 <sect1><tt>.IFP816</tt><label id=".IFP816"><p>
3129 Conditional assembly: Check if the assembler is currently in 65816 mode
3130 (see <tt><ref id=".P816" name=".P816"></tt> command).
3133 <sect1><tt>.IFPC02</tt><label id=".IFPC02"><p>
3135 Conditional assembly: Check if the assembler is currently in 65C02 mode
3136 (see <tt><ref id=".PC02" name=".PC02"></tt> command).
3139 <sect1><tt>.IFPSC02</tt><label id=".IFPSC02"><p>
3141 Conditional assembly: Check if the assembler is currently in 65SC02 mode
3142 (see <tt><ref id=".PSC02" name=".PSC02"></tt> command).
3145 <sect1><tt>.IFREF</tt><label id=".IFREF"><p>
3147 Conditional assembly: Check if a symbol is referenced. Must be followed
3148 by a symbol name. The condition is true if if the the given symbol was
3149 referenced before, and false otherwise.
3151 This command may be used to build subroutine libraries in include files
3152 (you may use separate object modules for this purpose too).
3157 .ifref ToHex ; If someone used this subroutine
3158 ToHex: tay ; Define subroutine
3164 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
3167 <sect1><tt>.IMPORT</tt><label id=".IMPORT"><p>
3169 Import a symbol from another module. The command is followed by a comma
3170 separated list of symbols to import, with each one optionally followed by
3171 an address specification.
3177 .import bar: zeropage
3180 See: <tt><ref id=".IMPORTZP" name=".IMPORTZP"></tt>
3183 <sect1><tt>.IMPORTZP</tt><label id=".IMPORTZP"><p>
3185 Import a symbol from another module. The command is followed by a comma
3186 separated list of symbols to import. The symbols are explicitly imported
3187 as zero page symbols (that is, symbols with values in byte range).
3195 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
3198 <sect1><tt>.INCBIN</tt><label id=".INCBIN"><p>
3200 Include a file as binary data. The command expects a string argument
3201 that is the name of a file to include literally in the current segment.
3202 In addition to that, a start offset and a size value may be specified,
3203 separated by commas. If no size is specified, all of the file from the
3204 start offset to end-of-file is used. If no start position is specified
3205 either, zero is assumed (which means that the whole file is inserted).
3210 ; Include whole file
3211 .incbin "sprites.dat"
3213 ; Include file starting at offset 256
3214 .incbin "music.dat", $100
3216 ; Read 100 bytes starting at offset 200
3217 .incbin "graphics.dat", 200, 100
3221 <sect1><tt>.INCLUDE</tt><label id=".INCLUDE"><p>
3223 Include another file. Include files may be nested up to a depth of 16.
3232 <sect1><tt>.INTERRUPTOR</tt><label id=".INTERRUPTOR"><p>
3234 Export a symbol and mark it as an interruptor. This may be used together
3235 with the linker to build a table of interruptor subroutines that are called
3238 Note: The linker has a feature to build a table of marked routines, but it
3239 is your code that must call these routines, so just declaring a symbol as
3240 interruptor does nothing by itself.
3242 An interruptor is always exported as an absolute (16 bit) symbol. You don't
3243 need to use an additional <tt/.export/ statement, this is implied by
3244 <tt/.interruptor/. It may have an optional priority that is separated by a
3245 comma. Higher numeric values mean a higher priority. If no priority is
3246 given, the default priority of 7 is used. Be careful when assigning
3247 priorities to your own module constructors so they won't interfere with the
3248 ones in the cc65 library.
3253 .interruptor IrqHandler
3254 .interruptor Handler, 16
3257 See the <tt><ref id=".CONDES" name=".CONDES"></tt> command and the separate
3258 section <ref id="condes" name="Module constructors/destructors"> explaining
3259 the feature in more detail.
3262 <sect1><tt>.ISMNEM, .ISMNEMONIC</tt><label id=".ISMNEMONIC"><p>
3264 Builtin function. The function expects an identifier as argument in braces.
3265 The argument is evaluated, and the function yields "true" if the identifier
3266 is defined as an instruction mnemonic that is recognized by the assembler.
3270 .if .not .ismnemonic(ina)
3279 <sect1><tt>.LINECONT</tt><label id=".LINECONT"><p>
3281 Switch on or off line continuations using the backslash character
3282 before a newline. The option is off by default.
3283 Note: Line continuations do not work in a comment. A backslash at the
3284 end of a comment is treated as part of the comment and does not trigger
3286 The command must be followed by a '+' or '-' character to switch the
3287 option on or off respectively.
3292 .linecont + ; Allow line continuations
3295 #$20 ; This is legal now
3299 <sect1><tt>.LIST</tt><label id=".LIST"><p>
3301 Enable output to the listing. The command must be followed by a boolean
3302 switch ("on", "off", "+" or "-") and will enable or disable listing
3304 The option has no effect if the listing is not enabled by the command line
3305 switch -l. If -l is used, an internal counter is set to 1. Lines are output
3306 to the listing file, if the counter is greater than zero, and suppressed if
3307 the counter is zero. Each use of <tt/.LIST/ will increment or decrement the
3313 .list on ; Enable listing output
3317 <sect1><tt>.LISTBYTES</tt><label id=".LISTBYTES"><p>
3319 Set, how many bytes are shown in the listing for one source line. The
3320 default is 12, so the listing will show only the first 12 bytes for any
3321 source line that generates more than 12 bytes of code or data.
3322 The directive needs an argument, which is either "unlimited", or an
3323 integer constant in the range 4..255.
3328 .listbytes unlimited ; List all bytes
3329 .listbytes 12 ; List the first 12 bytes
3330 .incbin "data.bin" ; Include large binary file
3334 <sect1><tt>.LOBYTES</tt><label id=".LOBYTES"><p>
3336 Define byte sized data by extracting only the low byte (that is, bits 0-7) from
3337 each expression. This is equivalent to <tt><ref id=".BYTE" name=".BYTE"></tt> with
3338 the operator '<' prepended to each expression in its list.
3343 .lobytes $1234, $2345, $3456, $4567
3344 .hibytes $fedc, $edcb, $dcba, $cba9
3347 which is equivalent to
3350 .byte $34, $45, $56, $67
3351 .byte $fe, $ed, $dc, $cb
3357 .define MyTable TableItem0, TableItem1, TableItem2, TableItem3
3359 TableLookupLo: .lobytes MyTable
3360 TableLookupHi: .hibytes MyTable
3363 which is equivalent to
3366 TableLookupLo: .byte <TableItem0, <TableItem1, <TableItem2, <TableItem3
3367 TableLookupHi: .byte >TableItem0, >TableItem1, >TableItem2, >TableItem3
3370 See also: <tt><ref id=".BYTE" name=".BYTE"></tt>,
3371 <tt><ref id=".HIBYTES" name=".HIBYTES"></tt>,
3372 <tt><ref id=".BANKBYTES" name=".BANKBYTES"></tt>
3375 <sect1><tt>.LOCAL</tt><label id=".LOCAL"><p>
3377 This command may only be used inside a macro definition. It declares a
3378 list of identifiers as local to the macro expansion.
3380 A problem when using macros are labels: Since they don't change their name,
3381 you get a "duplicate symbol" error if the macro is expanded the second time.
3382 Labels declared with <tt><ref id=".LOCAL" name=".LOCAL"></tt> have their
3383 name mapped to an internal unique name (<tt/___ABCD__/) with each macro
3386 Some other assemblers start a new lexical block inside a macro expansion.
3387 This has some drawbacks however, since that will not allow <em/any/ symbol
3388 to be visible outside a macro, a feature that is sometimes useful. The
3389 <tt><ref id=".LOCAL" name=".LOCAL"></tt> command is in my eyes a better way
3390 to address the problem.
3392 You get an error when using <tt><ref id=".LOCAL" name=".LOCAL"></tt> outside
3396 <sect1><tt>.LOCALCHAR</tt><label id=".LOCALCHAR"><p>
3398 Defines the character that start "cheap" local labels. You may use one
3399 of '@' and '?' as start character. The default is '@'.
3401 Cheap local labels are labels that are visible only between two non
3402 cheap labels. This way you can reuse identifiers like "<tt/loop/" without
3403 using explicit lexical nesting.
3410 Clear: lda #$00 ; Global label
3411 ?Loop: sta Mem,y ; Local label
3415 Sub: ... ; New global label
3416 bne ?Loop ; ERROR: Unknown identifier!
3420 <sect1><tt>.MACPACK</tt><label id=".MACPACK"><p>
3422 Insert a predefined macro package. The command is followed by an
3423 identifier specifying the macro package to insert. Available macro
3427 atari Defines the scrcode macro.
3428 cbm Defines the scrcode macro.
3429 cpu Defines constants for the .CPU variable.
3430 generic Defines generic macroes like add, sub, and blt.
3431 longbranch Defines conditional long-jump macroes.
3434 Including a macro package twice, or including a macro package that
3435 redefines already existing macros will lead to an error.
3440 .macpack longbranch ; Include macro package
3442 cmp #$20 ; Set condition codes
3443 jne Label ; Jump long on condition
3446 Macro packages are explained in more detail in section <ref
3447 id="macropackages" name="Macro packages">.
3450 <sect1><tt>.MAC, .MACRO</tt><label id=".MACRO"><p>
3452 Start a classic macro definition. The command is followed by an identifier
3453 (the macro name) and optionally by a comma separated list of identifiers
3454 that are macro parameters. A macro definition is terminated by <tt><ref
3455 id=".ENDMACRO" name=".ENDMACRO"></tt>.
3460 .macro ldax arg ; Define macro ldax
3465 See: <tt><ref id=".DELMACRO" name=".DELMACRO"></tt>,
3466 <tt><ref id=".ENDMACRO" name=".ENDMACRO"></tt>,
3467 <tt><ref id=".EXITMACRO" name=".EXITMACRO"></tt>
3469 See also section <ref id="macros" name="Macros">.
3472 <sect1><tt>.ORG</tt><label id=".ORG"><p>
3474 Start a section of absolute code. The command is followed by a constant
3475 expression that gives the new PC counter location for which the code is
3476 assembled. Use <tt><ref id=".RELOC" name=".RELOC"></tt> to switch back to
3479 By default, absolute/relocatable mode is global (valid even when switching
3480 segments). Using <tt>.FEATURE <ref id="org_per_seg" name="org_per_seg"></tt>
3481 it can be made segment local.
3483 Please note that you <em/do not need/ <tt/.ORG/ in most cases. Placing
3484 code at a specific address is the job of the linker, not the assembler, so
3485 there is usually no reason to assemble code to a specific address.
3490 .org $7FF ; Emit code starting at $7FF
3494 <sect1><tt>.OUT</tt><label id=".OUT"><p>
3496 Output a string to the console without producing an error. This command
3497 is similar to <tt/.ERROR/, however, it does not force an assembler error
3498 that prevents the creation of an object file.
3503 .out "This code was written by the codebuster(tm)"
3506 See also: <tt><ref id=".ERROR" name=".ERROR"></tt>,
3507 <tt><ref id=".FATAL" name=".FATAL"></tt>,
3508 <tt><ref id=".WARNING" name=".WARNING"></tt>
3511 <sect1><tt>.P02</tt><label id=".P02"><p>
3513 Enable the 6502 instruction set, disable 65SC02, 65C02 and 65816
3514 instructions. This is the default if not overridden by the
3515 <tt><ref id="option--cpu" name="--cpu"></tt> command line option.
3517 See: <tt><ref id=".PC02" name=".PC02"></tt>, <tt><ref id=".PSC02"
3518 name=".PSC02"></tt>, <tt><ref id=".P816" name=".P816"></tt> and
3519 <tt><ref id=".P4510" name=".P4510"></tt>
3522 <sect1><tt>.P4510</tt><label id=".P4510"><p>
3524 Enable the 4510 instruction set. This is a superset of the 65C02 and
3525 6502 instruction sets.
3527 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
3528 name=".PSC02"></tt>, <tt><ref id=".PC02" name=".PC02"></tt> and
3529 <tt><ref id=".P816" name=".P816"></tt>
3532 <sect1><tt>.P816</tt><label id=".P816"><p>
3534 Enable the 65816 instruction set. This is a superset of the 65SC02 and
3535 6502 instruction sets.
3537 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
3538 name=".PSC02"></tt>, <tt><ref id=".PC02" name=".PC02"></tt> and
3539 <tt><ref id=".P4510" name=".P4510"></tt>
3542 <sect1><tt>.PAGELEN, .PAGELENGTH</tt><label id=".PAGELENGTH"><p>
3544 Set the page length for the listing. Must be followed by an integer
3545 constant. The value may be "unlimited", or in the range 32 to 127. The
3546 statement has no effect if no listing is generated. The default value is -1
3547 (unlimited) but may be overridden by the <tt/--pagelength/ command line
3548 option. Beware: Since ca65 is a one pass assembler, the listing is generated
3549 after assembly is complete, you cannot use multiple line lengths with one
3550 source. Instead, the value set with the last <tt/.PAGELENGTH/ is used.
3555 .pagelength 66 ; Use 66 lines per listing page
3557 .pagelength unlimited ; Unlimited page length
3561 <sect1><tt>.PC02</tt><label id=".PC02"><p>
3563 Enable the 65C02 instructions set. This instruction set includes all
3564 6502 and 65SC02 instructions.
3566 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
3567 name=".PSC02"></tt>, <tt><ref id=".P816" name=".P816"></tt> and
3568 <tt><ref id=".P4510" name=".P4510"></tt>
3571 <sect1><tt>.POPCPU</tt><label id=".POPCPU"><p>
3573 Pop the last CPU setting from the stack, and activate it.
3575 This command will switch back to the CPU that was last pushed onto the CPU
3576 stack using the <tt><ref id=".PUSHCPU" name=".PUSHCPU"></tt> command, and
3577 remove this entry from the stack.
3579 The assembler will print an error message if the CPU stack is empty when
3580 this command is issued.
3582 See: <tt><ref id=".CPU" name=".CPU"></tt>, <tt><ref id=".PUSHCPU"
3583 name=".PUSHCPU"></tt>, <tt><ref id=".SETCPU" name=".SETCPU"></tt>
3586 <sect1><tt>.POPSEG</tt><label id=".POPSEG"><p>
3588 Pop the last pushed segment from the stack, and set it.
3590 This command will switch back to the segment that was last pushed onto the
3591 segment stack using the <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
3592 command, and remove this entry from the stack.
3594 The assembler will print an error message if the segment stack is empty
3595 when this command is issued.
3597 See: <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
3600 <sect1><tt>.PROC</tt><label id=".PROC"><p>
3602 Start a nested lexical level with the given name and adds a symbol with this
3603 name to the enclosing scope. All new symbols from now on are in the local
3604 lexical level and are accessible from outside only via <ref id="scopesyntax"
3605 name="explicit scope specification">. Symbols defined outside this local
3606 level may be accessed as long as their names are not used for new symbols
3607 inside the level. Symbols names in other lexical levels do not clash, so you
3608 may use the same names for identifiers. The lexical level ends when the
3609 <tt><ref id=".ENDPROC" name=".ENDPROC"></tt> command is read. Lexical levels
3610 may be nested up to a depth of 16 (this is an artificial limit to protect
3611 against errors in the source).
3613 Note: Macro names are always in the global level and in a separate name
3614 space. There is no special reason for this, it's just that I've never
3615 had any need for local macro definitions.
3620 .proc Clear ; Define Clear subroutine, start new level
3622 L1: sta Mem,y ; L1 is local and does not cause a
3623 ; duplicate symbol error if used in other
3626 bne L1 ; Reference local symbol
3628 .endproc ; Leave lexical level
3631 See: <tt/<ref id=".ENDPROC" name=".ENDPROC">/ and <tt/<ref id=".SCOPE"
3635 <sect1><tt>.PSC02</tt><label id=".PSC02"><p>
3637 Enable the 65SC02 instructions set. This instruction set includes all
3640 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PC02"
3641 name=".PC02"></tt>, <tt><ref id=".P816" name=".P816"></tt> and
3642 <tt><ref id=".P4510" name=".P4510"></tt>
3645 <sect1><tt>.PUSHCPU</tt><label id=".PUSHCPU"><p>
3647 Push the currently active CPU onto a stack. The stack has a size of 8
3650 <tt/.PUSHCPU/ allows together with <tt><ref id=".POPCPU"
3651 name=".POPCPU"></tt> to switch to another CPU and to restore the old CPU
3652 later, without knowledge of the current CPU setting.
3654 The assembler will print an error message if the CPU stack is already full,
3655 when this command is issued.
3657 See: <tt><ref id=".CPU" name=".CPU"></tt>, <tt><ref id=".POPCPU"
3658 name=".POPCPU"></tt>, <tt><ref id=".SETCPU" name=".SETCPU"></tt>
3661 <sect1><tt>.PUSHSEG</tt><label id=".PUSHSEG"><p>
3663 Push the currently active segment onto a stack. The entries on the stack
3664 include the name of the segment and the segment type. The stack has a size
3667 <tt/.PUSHSEG/ allows together with <tt><ref id=".POPSEG" name=".POPSEG"></tt>
3668 to switch to another segment and to restore the old segment later, without
3669 even knowing the name and type of the current segment.
3671 The assembler will print an error message if the segment stack is already
3672 full, when this command is issued.
3674 See: <tt><ref id=".POPSEG" name=".POPSEG"></tt>
3677 <sect1><tt>.RELOC</tt><label id=".RELOC"><p>
3679 Switch back to relocatable mode. See the <tt><ref id=".ORG"
3680 name=".ORG"></tt> command.
3683 <sect1><tt>.REPEAT</tt><label id=".REPEAT"><p>
3685 Repeat all commands between <tt/.REPEAT/ and <tt><ref id=".ENDREPEAT"
3686 name=".ENDREPEAT"></tt> constant number of times. The command is followed by
3687 a constant expression that tells how many times the commands in the body
3688 should get repeated. Optionally, a comma and an identifier may be specified.
3689 If this identifier is found in the body of the repeat statement, it is
3690 replaced by the current repeat count (starting with zero for the first time
3691 the body is repeated).
3693 <tt/.REPEAT/ statements may be nested. If you use the same repeat count
3694 identifier for a nested <tt/.REPEAT/ statement, the one from the inner
3695 level will be used, not the one from the outer level.
3699 The following macro will emit a string that is "encrypted" in that all
3700 characters of the string are XORed by the value $55.
3704 .repeat .strlen(Arg), I
3705 .byte .strat(Arg, I) ^ $55
3710 See: <tt><ref id=".ENDREPEAT" name=".ENDREPEAT"></tt>
3713 <sect1><tt>.RES</tt><label id=".RES"><p>
3715 Reserve storage. The command is followed by one or two constant
3716 expressions. The first one is mandatory and defines, how many bytes of
3717 storage should be defined. The second, optional expression must by a
3718 constant byte value that will be used as value of the data. If there
3719 is no fill value given, the linker will use the value defined in the
3720 linker configuration file (default: zero).
3725 ; Reserve 12 bytes of memory with value $AA
3730 <sect1><tt>.RODATA</tt><label id=".RODATA"><p>
3732 Switch to the RODATA segment. The name of the RODATA segment is always
3733 "RODATA", so this is a shortcut for
3739 The RODATA segment is a segment that is used by the compiler for
3740 readonly data like string constants.
3742 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
3745 <sect1><tt>.SCOPE</tt><label id=".SCOPE"><p>
3747 Start a nested lexical level with the given name. All new symbols from now
3748 on are in the local lexical level and are accessible from outside only via
3749 <ref id="scopesyntax" name="explicit scope specification">. Symbols defined
3750 outside this local level may be accessed as long as their names are not used
3751 for new symbols inside the level. Symbols names in other lexical levels do
3752 not clash, so you may use the same names for identifiers. The lexical level
3753 ends when the <tt><ref id=".ENDSCOPE" name=".ENDSCOPE"></tt> command is
3754 read. Lexical levels may be nested up to a depth of 16 (this is an
3755 artificial limit to protect against errors in the source).
3757 Note: Macro names are always in the global level and in a separate name
3758 space. There is no special reason for this, it's just that I've never
3759 had any need for local macro definitions.
3764 .scope Error ; Start new scope named Error
3766 File = 1 ; File error
3767 Parse = 2 ; Parse error
3768 .endscope ; Close lexical level
3771 lda #Error::File ; Use symbol from scope Error
3774 See: <tt/<ref id=".ENDSCOPE" name=".ENDSCOPE">/ and <tt/<ref id=".PROC"
3778 <sect1><tt>.SEGMENT</tt><label id=".SEGMENT"><p>
3780 Switch to another segment. Code and data is always emitted into a
3781 segment, that is, a named section of data. The default segment is
3782 "CODE". There may be up to 254 different segments per object file
3783 (and up to 65534 per executable). There are shortcut commands for
3784 the most common segments ("ZEROPAGE", "CODE", "RODATA", "DATA", and "BSS").
3786 The command is followed by a string containing the segment name (there are
3787 some constraints for the name - as a rule of thumb use only those segment
3788 names that would also be valid identifiers). There may also be an optional
3789 address size separated by a colon. See the section covering <tt/<ref
3790 id="address-sizes" name="address sizes">/ for more information.
3792 The default address size for a segment depends on the memory model specified
3793 on the command line. The default is "absolute", which means that you don't
3794 have to use an address size modifier in most cases.
3796 "absolute" means that the is a segment with 16 bit (absolute) addressing.
3797 That is, the segment will reside somewhere in core memory outside the zero
3798 page. "zeropage" (8 bit) means that the segment will be placed in the zero
3799 page and direct (short) addressing is possible for data in this segment.
3801 Beware: Only labels in a segment with the zeropage attribute are marked
3802 as reachable by short addressing. The `*' (PC counter) operator will
3803 work as in other segments and will create absolute variable values.
3805 Please note that a segment cannot have two different address sizes. A
3806 segment specified as zeropage cannot be declared as being absolute later.
3811 .segment "ROM2" ; Switch to ROM2 segment
3812 .segment "ZP2": zeropage ; New direct segment
3813 .segment "ZP2" ; Ok, will use last attribute
3814 .segment "ZP2": absolute ; Error, redecl mismatch
3817 See: <tt><ref id=".BSS" name=".BSS"></tt>, <tt><ref id=".CODE"
3818 name=".CODE"></tt>, <tt><ref id=".DATA" name=".DATA"></tt>, <tt><ref
3819 id=".RODATA" name=".RODATA"></tt>, and <tt><ref id=".ZEROPAGE"
3820 name=".ZEROPAGE"></tt>
3823 <sect1><tt>.SET</tt><label id=".SET"><p>
3825 <tt/.SET/ is used to assign a value to a variable. See <ref id="variables"
3826 name="Numeric variables"> for a full description.
3829 <sect1><tt>.SETCPU</tt><label id=".SETCPU"><p>
3831 Switch the CPU instruction set. The command is followed by a string that
3832 specifies the CPU. Possible values are those that can also be supplied to
3833 the <tt><ref id="option--cpu" name="--cpu"></tt> command line option,
3834 namely: 6502, 6502X, 65SC02, 65C02, 65816, 4510 and HuC6280.
3836 See: <tt><ref id=".CPU" name=".CPU"></tt>,
3837 <tt><ref id=".IFP02" name=".IFP02"></tt>,
3838 <tt><ref id=".IFP816" name=".IFP816"></tt>,
3839 <tt><ref id=".IFPC02" name=".IFPC02"></tt>,
3840 <tt><ref id=".IFPSC02" name=".IFPSC02"></tt>,
3841 <tt><ref id=".P02" name=".P02"></tt>,
3842 <tt><ref id=".P816" name=".P816"></tt>,
3843 <tt><ref id=".P4510" name=".P4510"></tt>,
3844 <tt><ref id=".PC02" name=".PC02"></tt>,
3845 <tt><ref id=".PSC02" name=".PSC02"></tt>
3848 <sect1><tt>.SMART</tt><label id=".SMART"><p>
3850 Switch on or off smart mode. The command must be followed by a '+' or '-'
3851 character to switch the option on or off respectively. The default is off
3852 (that is, the assembler doesn't try to be smart), but this default may be
3853 changed by the -s switch on the command line.
3855 In smart mode the assembler will do the following:
3858 <item>Track usage of the <tt/REP/ and <tt/SEP/ instructions in 65816 mode
3859 and update the operand sizes accordingly. If the operand of such an
3860 instruction cannot be evaluated by the assembler (for example, because
3861 the operand is an imported symbol), a warning is issued. Beware: Since
3862 the assembler cannot trace the execution flow this may lead to false
3863 results in some cases. If in doubt, use the <tt/.Inn/ and <tt/.Ann/
3864 instructions to tell the assembler about the current settings.
3865 <item>In 65816 mode, replace a <tt/RTS/ instruction by <tt/RTL/ if it is
3866 used within a procedure declared as <tt/far/, or if the procedure has
3867 no explicit address specification, but it is <tt/far/ because of the
3875 .smart - ; Stop being smart
3878 See: <tt><ref id=".A16" name=".A16"></tt>,
3879 <tt><ref id=".A8" name=".A8"></tt>,
3880 <tt><ref id=".I16" name=".I16"></tt>,
3881 <tt><ref id=".I8" name=".I8"></tt>
3884 <sect1><tt>.STRUCT</tt><label id=".STRUCT"><p>
3886 Starts a struct definition. Structs are covered in a separate section named
3887 <ref id="structs" name=""Structs and unions"">.
3889 See also: <tt><ref id=".ENDSTRUCT" name=".ENDSTRUCT"></tt>,
3890 <tt><ref id=".ENDUNION" name=".ENDUNION"></tt>,
3891 <tt><ref id=".UNION" name=".UNION"></tt>
3894 <sect1><tt>.TAG</tt><label id=".TAG"><p>
3896 Allocate space for a struct or union.
3907 .tag Point ; Allocate 4 bytes
3911 <sect1><tt>.UNDEF, .UNDEFINE</tt><label id=".UNDEFINE"><p>
3913 Delete a define style macro definition. The command is followed by an
3914 identifier which specifies the name of the macro to delete. Macro
3915 replacement is switched of when reading the token following the command
3916 (otherwise the macro name would be replaced by its replacement list).
3918 See also the <tt><ref id=".DEFINE" name=".DEFINE"></tt> command and
3919 section <ref id="macros" name="Macros">.
3922 <sect1><tt>.UNION</tt><label id=".UNION"><p>
3924 Starts a union definition. Unions are covered in a separate section named
3925 <ref id="structs" name=""Structs and unions"">.
3927 See also: <tt><ref id=".ENDSTRUCT" name=".ENDSTRUCT"></tt>,
3928 <tt><ref id=".ENDUNION" name=".ENDUNION"></tt>,
3929 <tt><ref id=".STRUCT" name=".STRUCT"></tt>
3932 <sect1><tt>.WARNING</tt><label id=".WARNING"><p>
3934 Force an assembly warning. The assembler will output a warning message
3935 preceded by "User warning". This warning will always be output, even if
3936 other warnings are disabled with the <tt><ref id="option-W" name="-W0"></tt>
3937 command line option.
3939 This command may be used to output possible problems when assembling
3948 .warning "Forward jump in jne, cannot optimize!"
3958 See also: <tt><ref id=".ERROR" name=".ERROR"></tt>,
3959 <tt><ref id=".FATAL" name=".FATAL"></tt>,
3960 <tt><ref id=".OUT" name=".OUT"></tt>
3963 <sect1><tt>.WORD</tt><label id=".WORD"><p>
3965 Define word sized data. Must be followed by a sequence of (word ranged,
3966 but not necessarily constant) expressions.
3971 .word $0D00, $AF13, _Clear
3975 <sect1><tt>.ZEROPAGE</tt><label id=".ZEROPAGE"><p>
3977 Switch to the ZEROPAGE segment and mark it as direct (zeropage) segment.
3978 The name of the ZEROPAGE segment is always "ZEROPAGE", so this is a
3982 .segment "ZEROPAGE": zeropage
3985 Because of the "zeropage" attribute, labels declared in this segment are
3986 addressed using direct addressing mode if possible. You <em/must/ instruct
3987 the linker to place this segment somewhere in the address range 0..$FF
3988 otherwise you will get errors.
3990 See: <tt><ref id=".SEGMENT" name=".SEGMENT"></tt>
3994 <sect>Macros<label id="macros"><p>
3997 <sect1>Introduction<p>
3999 Macros may be thought of as "parametrized super instructions". Macros are
4000 sequences of tokens that have a name. If that name is used in the source
4001 file, the macro is "expanded", that is, it is replaced by the tokens that
4002 were specified when the macro was defined.
4005 <sect1>Macros without parameters<p>
4007 In its simplest form, a macro does not have parameters. Here's an
4011 .macro asr ; Arithmetic shift right
4012 cmp #$80 ; Put bit 7 into carry
4013 ror ; Rotate right with carry
4017 The macro above consists of two real instructions, that are inserted into
4018 the code, whenever the macro is expanded. Macro expansion is simply done
4019 by using the name, like this:
4028 <sect1>Parametrized macros<p>
4030 When using macro parameters, macros can be even more useful:
4044 When calling the macro, you may give a parameter, and each occurrence of
4045 the name "addr" in the macro definition will be replaced by the given
4064 A macro may have more than one parameter, in this case, the parameters
4065 are separated by commas. You are free to give less parameters than the
4066 macro actually takes in the definition. You may also leave intermediate
4067 parameters empty. Empty parameters are replaced by empty space (that is,
4068 they are removed when the macro is expanded). If you have a look at our
4069 macro definition above, you will see, that replacing the "addr" parameter
4070 by nothing will lead to wrong code in most lines. To help you, writing
4071 macros with a variable parameter list, there are some control commands:
4073 <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> tests the rest of the line and
4074 returns true, if there are any tokens on the remainder of the line. Since
4075 empty parameters are replaced by nothing, this may be used to test if a given
4076 parameter is empty. <tt><ref id=".IFNBLANK" name=".IFNBLANK"></tt> tests the
4079 Look at this example:
4082 .macro ldaxy a, x, y
4095 That macro may be called as follows:
4098 ldaxy 1, 2, 3 ; Load all three registers
4100 ldaxy 1, , 3 ; Load only a and y
4102 ldaxy , , 3 ; Load y only
4105 There's another helper command for determining which macro parameters are
4106 valid: <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt>. That command is
4107 replaced by the parameter count given, <em/including/ explicitly empty
4111 ldaxy 1 ; .PARAMCOUNT = 1
4112 ldaxy 1,,3 ; .PARAMCOUNT = 3
4113 ldaxy 1,2 ; .PARAMCOUNT = 2
4114 ldaxy 1, ; .PARAMCOUNT = 2
4115 ldaxy 1,2,3 ; .PARAMCOUNT = 3
4118 Macro parameters may optionally be enclosed into curly braces. This allows the
4119 inclusion of tokens that would otherwise terminate the parameter (the comma in
4120 case of a macro parameter).
4123 .macro foo arg1, arg2
4127 foo ($00,x) ; Two parameters passed
4128 foo {($00,x)} ; One parameter passed
4131 In the first case, the macro is called with two parameters: '<tt/($00/'
4132 and '<tt/x)/'. The comma is not passed to the macro, because it is part of the
4133 calling sequence, not the parameters.
4135 In the second case, '<tt/($00,x)/' is passed to the macro; this time,
4136 including the comma.
4139 <sect1>Detecting parameter types<p>
4141 Sometimes it is nice to write a macro that acts differently depending on the
4142 type of the argument supplied. An example would be a macro that loads a 16 bit
4143 value from either an immediate operand, or from memory. The <tt/<ref
4144 id=".MATCH" name=".MATCH">/ and <tt/<ref id=".XMATCH" name=".XMATCH">/
4145 functions will allow you to do exactly this:
4149 .if (.match (.left (1, {arg}), #))
4151 lda #<(.right (.tcount ({arg})-1, {arg}))
4152 ldx #>(.right (.tcount ({arg})-1, {arg}))
4154 ; assume absolute or zero page
4161 Using the <tt/<ref id=".MATCH" name=".MATCH">/ function, the macro is able to
4162 check if its argument begins with a hash mark. If so, two immediate loads are
4163 emitted, Otherwise a load from an absolute zero page memory location is
4164 assumed. Please note how the curly braces are used to enclose parameters to
4165 pseudo functions handling token lists. This is necessary, because the token
4166 lists may include commas or parens, which would be treated by the assembler
4169 The macro can be used as
4174 ldax #$1234 ; X=$12, A=$34
4176 ldax foo ; X=$56, A=$78
4180 <sect1>Recursive macros<p>
4182 Macros may be used recursively:
4185 .macro push r1, r2, r3
4194 There's also a special macro command to help with writing recursive macros:
4195 <tt><ref id=".EXITMACRO" name=".EXITMACRO"></tt>. That command will stop macro
4196 expansion immediately:
4199 .macro push r1, r2, r3, r4, r5, r6, r7
4201 ; First parameter is empty
4207 push r2, r3, r4, r5, r6, r7
4211 When expanding that macro, the expansion will push all given parameters
4212 until an empty one is encountered. The macro may be called like this:
4215 push $20, $21, $32 ; Push 3 ZP locations
4216 push $21 ; Push one ZP location
4220 <sect1>Local symbols inside macros<p>
4222 Now, with recursive macros, <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> and
4223 <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt>, what else do you need?
4224 Have a look at the inc16 macro above. Here is it again:
4238 If you have a closer look at the code, you will notice, that it could be
4239 written more efficiently, like this:
4250 But imagine what happens, if you use this macro twice? Since the label "Skip"
4251 has the same name both times, you get a "duplicate symbol" error. Without a
4252 way to circumvent this problem, macros are not as useful, as they could be.
4253 One possible solution is the command <tt><ref id=".LOCAL" name=".LOCAL"></tt>.
4254 It declares one or more symbols as local to the macro expansion. The names of
4255 local variables are replaced by a unique name in each separate macro
4256 expansion. So we can solve the problem above by using <tt/.LOCAL/:
4260 .local Skip ; Make Skip a local symbol
4264 Skip: ; Not visible outside
4268 Another solution is of course to start a new lexical block inside the macro
4269 that hides any labels:
4283 <sect1>C style macros<p>
4285 Starting with version 2.5 of the assembler, there is a second macro type
4286 available: C style macros using the <tt/.DEFINE/ directive. These macros are
4287 similar to the classic macro type described above, but behaviour is sometimes
4292 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> may not
4293 span more than a line. You may use line continuation (see <tt><ref
4294 id=".LINECONT" name=".LINECONT"></tt>) to spread the definition over
4295 more than one line for increased readability, but the macro itself
4296 may not contain an end-of-line token.
4298 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> share
4299 the name space with classic macros, but they are detected and replaced
4300 at the scanner level. While classic macros may be used in every place,
4301 where a mnemonic or other directive is allowed, <tt><ref id=".DEFINE"
4302 name=".DEFINE"></tt> style macros are allowed anywhere in a line. So
4303 they are more versatile in some situations.
4305 <item> <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may take
4306 parameters. While classic macros may have empty parameters, this is
4307 not true for <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros.
4308 For this macro type, the number of actual parameters must match
4309 exactly the number of formal parameters.
4311 To make this possible, formal parameters are enclosed in braces when
4312 defining the macro. If there are no parameters, the empty braces may
4315 <item> Since <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may not
4316 contain end-of-line tokens, there are things that cannot be done. They
4317 may not contain several processor instructions for example. So, while
4318 some things may be done with both macro types, each type has special
4319 usages. The types complement each other.
4321 <item> Parentheses work differently from C macros.
4322 The common practice of wrapping C macros in parentheses may cause
4323 unintended problems here, such as accidentally implying an
4324 indirect addressing mode. While the definition of a macro requires
4325 parentheses around its argument list, when invoked they should not be
4330 Let's look at a few examples to make the advantages and disadvantages
4333 To emulate assemblers that use "<tt/EQU/" instead of "<tt/=/" you may use the
4334 following <tt/.DEFINE/:
4339 foo EQU $1234 ; This is accepted now
4342 You may use the directive to define string constants used elsewhere:
4345 ; Define the version number
4346 .define VERSION "12.3a"
4352 Macros with parameters may also be useful:
4355 .define DEBUG(message) .out message
4357 DEBUG "Assembling include file #3"
4360 Note that, while formal parameters have to be placed in parentheses,
4361 the actual argument used when invoking the macro should not be.
4362 The invoked arguments are separated by commas only, if parentheses are
4363 used by accident they will become part of the replaced token.
4365 If you wish to have an expression follow the macro invocation, the
4366 last parameter can be enclosed in curly braces {} to indicate the end of that
4372 .define COMBINE(ta,tb,tc) ta+tb*10+tc*100
4374 .word COMBINE 5,6,7 ; 5+6*10+7*100 = 765
4375 .word COMBINE(5,6,7) ; (5+6*10+7)*100 = 7200 ; incorrect use of parentheses
4376 .word COMBINE 5,6,7+1 ; 5+6*10+7+1*100 = 172
4377 .word COMBINE 5,6,{7}+1 ; 5+6*10+7*100+1 = 766 ; {} encloses the argument
4378 .word COMBINE 5,6-2,7 ; 5+6-2*10+7*100 = 691
4379 .word COMBINE 5,(6-2),7 ; 5+(6-2)*10+7*100 = 745
4380 .word COMBINE 5,6,7+COMBINE 0,1,2 ; 5+6*10+7+0+1*10+2*100*100 = 20082
4381 .word COMBINE 5,6,{7}+COMBINE 0,1,2 ; 5+6*10+7*100+0+1*10+2*100 = 975
4384 With C macros it is common to enclose the results in parentheses to
4385 prevent unintended interactions with the text of the arguments, but
4386 additional care must be taken in this assembly context where parentheses
4387 may alter the meaning of a statement. In particular, indirect addressing modes
4388 may be accidentally implied:
4391 .define DUO(ta,tb) (ta+(tb*10))
4393 lda DUO(5,4), Y ; LDA (indirect), Y
4394 lda 0+DUO(5,4), Y ; LDA absolute indexed, Y
4398 <sect1>Characters in macros<p>
4400 When using the <ref id="option-t" name="-t"> option, characters are translated
4401 into the target character set of the specific machine. However, this happens
4402 as late as possible. This means that strings are translated if they are part
4403 of a <tt><ref id=".BYTE" name=".BYTE"></tt> or <tt><ref id=".ASCIIZ"
4404 name=".ASCIIZ"></tt> command. Characters are translated as soon as they are
4405 used as part of an expression.
4407 This behaviour is very intuitive outside of macros but may be confusing when
4408 doing more complex macros. If you compare characters against numeric values,
4409 be sure to take the translation into account.
4412 <sect1>Deleting macros<p>
4414 Macros can be deleted. This will not work if the macro that should be deleted
4415 is currently expanded as in the following non-working example:
4419 .delmacro notworking
4422 notworking ; Will not work
4425 The commands to delete classic and define style macros differ. Classic macros
4426 can be deleted by use of <tt><ref id=".DELMACRO" name=".DELMACRO"></tt>, while
4427 for <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros, <tt><ref
4428 id=".UNDEFINE" name=".UNDEFINE"></tt> must be used. Example:
4436 .byte value ; Emit one byte with value 1
4437 mac ; Emit another byte with value 2
4442 .byte value ; Error: Unknown identifier
4443 mac ; Error: Missing ":"
4446 A separate command for <tt>.DEFINE</tt> style macros was necessary, because
4447 the name of such a macro is replaced by its replacement list on a very low
4448 level. To get the actual name, macro replacement has to be switched off when
4449 reading the argument to <tt>.UNDEFINE</tt>. This does also mean that the
4450 argument to <tt>.UNDEFINE</tt> is not allowed to come from another
4451 <tt>.DEFINE</tt>. All this is not necessary for classic macros, so having two
4452 different commands increases flexibility.
4456 <sect>Macro packages<label id="macropackages"><p>
4458 Using the <tt><ref id=".MACPACK" name=".MACPACK"></tt> directive, predefined
4459 macro packages may be included with just one command. Available macro packages
4463 <sect1><tt>.MACPACK generic</tt><p>
4465 This macro package defines macroes that are useful in almost any program.
4466 Currently defined macroes are:
4469 .macro add Arg ; add without carry
4474 .macro sub Arg ; subtract without borrow
4479 .macro bge Arg ; branch on greater-than or equal
4483 .macro blt Arg ; branch on less-than
4487 .macro bgt Arg ; branch on greater-than
4494 .macro ble Arg ; branch on less-than or equal
4499 .macro bnz Arg ; branch on not zero
4503 .macro bze Arg ; branch on zero
4509 <sect1><tt>.MACPACK longbranch</tt><p>
4511 This macro package defines long conditional jumps. They are named like the
4512 short counterpart but with the 'b' replaced by a 'j'. Here is a sample
4513 definition for the "<tt/jeq/" macro, the other macros are built using the same
4518 .if .def(Target) .and ((*+2)-(Target) <= 127)
4527 All macros expand to a short branch, if the label is already defined (back
4528 jump) and is reachable with a short jump. Otherwise the macro expands to a
4529 conditional branch with the branch condition inverted, followed by an absolute
4530 jump to the actual branch target.
4532 The package defines the following macros:
4535 jeq, jne, jmi, jpl, jcs, jcc, jvs, jvc
4540 <sect1><tt>.MACPACK apple2</tt><p>
4542 This macro package defines a macro named <tt/scrcode/. It takes a string
4543 as argument and places this string into memory translated into screen codes.
4546 <sect1><tt>.MACPACK atari</tt><p>
4548 This macro package defines a macro named <tt/scrcode/. It takes a string
4549 as argument and places this string into memory translated into screen codes.
4552 <sect1><tt>.MACPACK cbm</tt><p>
4554 This macro package defines a macro named <tt/scrcode/. It takes a string
4555 as argument and places this string into memory translated into screen codes.
4558 <sect1><tt>.MACPACK cpu</tt><p>
4560 This macro package does not define any macros but constants used to examine
4561 the value read from the <tt/<ref id=".CPU" name=".CPU">/ pseudo variable. For
4562 each supported CPU a constant similar to
4574 is defined. These constants may be used to determine the exact type of the
4575 currently enabled CPU. In addition to that, for each CPU instruction set,
4576 another constant is defined:
4588 The value read from the <tt/<ref id=".CPU" name=".CPU">/ pseudo variable may
4589 be checked with <tt/<ref id="operators" name=".BITAND">/ to determine if the
4590 currently enabled CPU supports a specific instruction set. For example the
4591 65C02 supports all instructions of the 65SC02 CPU, so it has the
4592 <tt/CPU_ISET_65SC02/ bit set in addition to its native <tt/CPU_ISET_65C02/
4596 .if (.cpu .bitand CPU_ISET_65SC02)
4604 it is possible to determine if the
4610 instruction is supported, which is the case for the 65SC02, 65C02 and 65816
4611 CPUs (the latter two are upwards compatible to the 65SC02).
4614 <sect1><tt>.MACPACK module</tt><p>
4616 This macro package defines a macro named <tt/module_header/. It takes an
4617 identifier as argument and is used to define the header of a module both
4618 in the dynamic and static variant.
4622 <sect>Predefined constants<label id="predefined-constants"><p>
4624 For better orthogonality, the assembler defines similar symbols as the
4625 compiler, depending on the target system selected:
4628 <item><tt/__APPLE2__/ - Target system is <tt/apple2/ or <tt/apple2enh/
4629 <item><tt/__APPLE2ENH__/ - Target system is <tt/apple2enh/
4630 <item><tt/__ATARI2600__/ - Target system is <tt/atari2600/
4631 <item><tt/__ATARI5200__/ - Target system is <tt/atari5200/
4632 <item><tt/__ATARI__/ - Target system is <tt/atari/ or <tt/atarixl/
4633 <item><tt/__ATARIXL__/ - Target system is <tt/atarixl/
4634 <item><tt/__ATMOS__/ - Target system is <tt/atmos/
4635 <item><tt/__BBC__/ - Target system is <tt/bbc/
4636 <item><tt/__C128__/ - Target system is <tt/c128/
4637 <item><tt/__C16__/ - Target system is <tt/c16/ or <tt/plus4/
4638 <item><tt/__C64__/ - Target system is <tt/c64/
4639 <item><tt/__CBM__/ - Target is a Commodore system
4640 <item><tt/__CBM510__/ - Target system is <tt/cbm510/
4641 <item><tt/__CBM610__/ - Target system is <tt/cbm610/
4642 <item><tt/__GEOS__/ - Target is a GEOS system
4643 <item><tt/__GEOS_APPLE__/ - Target system is <tt/geos-apple/
4644 <item><tt/__GEOS_CBM__/ - Target system is <tt/geos-cbm/
4645 <item><tt/__LUNIX__/ - Target system is <tt/lunix/
4646 <item><tt/__LYNX__/ - Target system is <tt/lynx/
4647 <item><tt/__NES__/ - Target system is <tt/nes/
4648 <item><tt/__OSIC1P__/ - Target system is <tt/osic1p/
4649 <item><tt/__PET__/ - Target system is <tt/pet/
4650 <item><tt/__PLUS4__/ - Target system is <tt/plus4/
4651 <item><tt/__SIM6502__/ - Target system is <tt/sim6502/
4652 <item><tt/__SIM65C02__/ - Target system is <tt/sim65c02/
4653 <item><tt/__SUPERVISION__/ - Target system is <tt/supervision/
4654 <item><tt/__VIC20__/ - Target system is <tt/vic20/
4658 <sect>Structs and unions<label id="structs"><p>
4660 <sect1>Structs and unions Overview<p>
4662 Structs and unions are special forms of <ref id="scopes" name="scopes">. They
4663 are to some degree comparable to their C counterparts. Both have a list of
4664 members. Each member allocates storage and may optionally have a name, which,
4665 in case of a struct, is the offset from the beginning and, in case of a union,
4669 <sect1>Declaration<p>
4671 Here is an example for a very simple struct with two members and a total size
4681 A union shares the total space between all its members, its size is the same
4682 as that of the largest member. The offset of all members relative to the union
4692 A struct or union must not necessarily have a name. If it is anonymous, no
4693 local scope is opened, the identifiers used to name the members are placed
4694 into the current scope instead.
4696 A struct may contain unnamed members and definitions of local structs. The
4697 storage allocators may contain a multiplier, as in the example below:
4702 .word 2 ; Allocate two words
4709 <sect1>The <tt/.TAG/ keyword<p>
4711 Using the <ref id=".TAG" name=".TAG"> keyword, it is possible to reserve space
4712 for an already defined struct or unions within another struct:
4726 Space for a struct or union may be allocated using the <ref id=".TAG"
4727 name=".TAG"> directive.
4733 Currently, members are just offsets from the start of the struct or union. To
4734 access a field of a struct, the member offset has to be added to the address
4735 of the struct itself:
4738 lda C+Circle::Radius ; Load circle radius into A
4741 This may change in a future version of the assembler.
4744 <sect1>Limitations<p>
4746 Structs and unions are currently implemented as nested symbol tables (in fact,
4747 they were a by-product of the improved scoping rules). Currently, the
4748 assembler has no idea of types. This means that the <ref id=".TAG"
4749 name=".TAG"> keyword will only allocate space. You won't be able to initialize
4750 variables declared with <ref id=".TAG" name=".TAG">, and adding an embedded
4751 structure to another structure with <ref id=".TAG" name=".TAG"> will not make
4752 this structure accessible by using the '::' operator.
4756 <sect>Module constructors/destructors<label id="condes"><p>
4758 <em>Note:</em> This section applies mostly to C programs, so the explanation
4759 below uses examples from the C libraries. However, the feature may also be
4760 useful for assembler programs.
4763 <sect1>Module constructors/destructors Overview<p>
4765 Using the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
4766 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
4767 name=".INTERRUPTOR"></tt> keywords it is possible to export functions in a
4768 special way. The linker is able to generate tables with all functions of a
4769 specific type. Such a table will <em>only</em> include symbols from object
4770 files that are linked into a specific executable. This may be used to add
4771 initialization and cleanup code for library modules, or a table of interrupt
4774 The C heap functions are an example where module initialization code is used.
4775 All heap functions (<tt>malloc</tt>, <tt>free</tt>, ...) work with a few
4776 variables that contain the start and the end of the heap, pointers to the free
4777 list and so on. Since the end of the heap depends on the size and start of the
4778 stack, it must be initialized at runtime. However, initializing these
4779 variables for programs that do not use the heap are a waste of time and
4782 So the central module defines a function that contains initialization code and
4783 exports this function using the <tt/.CONSTRUCTOR/ statement. If (and only if)
4784 this module is added to an executable by the linker, the initialization
4785 function will be placed into the table of constructors by the linker. The C
4786 startup code will call all constructors before <tt/main/ and all destructors
4787 after <tt/main/, so without any further work, the heap initialization code is
4788 called once the module is linked in.
4790 While it would be possible to add explicit calls to initialization functions
4791 in the startup code, the new approach has several advantages:
4795 If a module is not included, the initialization code is not linked in and not
4796 called. So you don't pay for things you don't need.
4799 Adding another library that needs initialization does not mean that the
4800 startup code has to be changed. Before we had module constructors and
4801 destructors, the startup code for all systems had to be adjusted to call the
4802 new initialization code.
4805 The feature saves memory: Each additional initialization function needs just
4806 two bytes in the table (a pointer to the function).
4811 <sect1>Calling order<p>
4813 The symbols are sorted in increasing priority order by the linker when using
4814 one of the builtin linker configurations, so the functions with lower
4815 priorities come first and are followed by those with higher priorities. The C
4816 library runtime subroutine that walks over the function tables calls the
4817 functions starting from the top of the table - which means that functions with
4818 a high priority are called first.
4820 So when using the C runtime, functions are called with high priority functions
4821 first, followed by low priority functions.
4826 When using these special symbols, please take care of the following:
4831 The linker will only generate function tables, it will not generate code to
4832 call these functions. If you're using the feature in some other than the
4833 existing C environments, you have to write code to call all functions in a
4834 linker generated table yourself. See the <tt/condes/ and <tt/callirq/ modules
4835 in the C runtime for an example on how to do this.
4838 The linker will only add addresses of functions that are in modules linked to
4839 the executable. This means that you have to be careful where to place the
4840 condes functions. If initialization or an irq handler is needed for a group of
4841 functions, be sure to place the function into a module that is linked in
4842 regardless of which function is called by the user.
4845 The linker will generate the tables only when requested to do so by the
4846 <tt/FEATURE CONDES/ statement in the linker config file. Each table has to
4847 be requested separately.
4850 Constructors and destructors may have priorities. These priorities determine
4851 the order of the functions in the table. If your initialization or cleanup code
4852 does depend on other initialization or cleanup code, you have to choose the
4853 priority for the functions accordingly.
4856 Besides the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
4857 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
4858 name=".INTERRUPTOR"></tt> statements, there is also a more generic command:
4859 <tt><ref id=".CONDES" name=".CONDES"></tt>. This allows to specify an
4860 additional type. Predefined types are 0 (constructor), 1 (destructor) and 2
4861 (interruptor). The linker generates a separate table for each type on request.
4866 <sect>Porting sources from other assemblers<p>
4868 Sometimes it is necessary to port code written for older assemblers to ca65.
4869 In some cases, this can be done without any changes to the source code by
4870 using the emulation features of ca65 (see <tt><ref id=".FEATURE"
4871 name=".FEATURE"></tt>). In other cases, it is necessary to make changes to the
4874 Probably the biggest difference is the handling of the <tt><ref id=".ORG"
4875 name=".ORG"></tt> directive. ca65 generates relocatable code, and placement is
4876 done by the linker. Most other assemblers generate absolute code, placement is
4877 done within the assembler and there is no external linker.
4879 In general it is not a good idea to write new code using the emulation
4880 features of the assembler, but there may be situations where even this rule is
4885 You need to use some of the ca65 emulation features to simulate the behaviour
4886 of such simple assemblers.
4889 <item>Prepare your sourcecode like this:
4892 ; if you want TASS style labels without colons
4893 .feature labels_without_colons
4895 ; if you want TASS style character constants
4896 ; ("a" instead of the default 'a')
4897 .feature loose_char_term
4899 .word *+2 ; the cbm load address
4904 notice that the two emulation features are mostly useful for porting
4905 sources originally written in/for TASS, they are not needed for the
4906 actual "simple assembler operation" and are not recommended if you are
4907 writing new code from scratch.
4909 <item>Replace all program counter assignments (which are not possible in ca65
4910 by default, and the respective emulation feature works different from what
4911 you'd expect) by another way to skip to memory locations, for example the
4912 <tt><ref id=".RES" name=".RES"></tt> directive.
4916 .res $2000-* ; reserve memory up to $2000
4919 Please note that other than the original TASS, ca65 can never move the program
4920 counter backwards - think of it as if you are assembling to disk with TASS.
4922 <item>Conditional assembly (<tt/.ifeq//<tt/.endif//<tt/.goto/ etc.) must be
4923 rewritten to match ca65 syntax. Most importantly notice that due to the lack
4924 of <tt/.goto/, everything involving loops must be replaced by
4925 <tt><ref id=".REPEAT" name=".REPEAT"></tt>.
4927 <item>To assemble code to a different address than it is executed at, use the
4928 <tt><ref id=".ORG" name=".ORG"></tt> directive instead of
4929 <tt/.offs/-constructs.
4936 .reloc ; back to normal
4939 <item>Then assemble like this:
4942 cl65 --start-addr 0x0ffe -t none myprog.s -o myprog.prg
4945 Note that you need to use the actual start address minus two, since two bytes
4946 are used for the cbm load address.
4953 ca65 (and all cc65 binutils) are (C) Copyright 1998-2003 Ullrich von
4954 Bassewitz. For usage of the binaries and/or sources the following
4955 conditions do apply:
4957 This software is provided 'as-is', without any expressed or implied
4958 warranty. In no event will the authors be held liable for any damages
4959 arising from the use of this software.
4961 Permission is granted to anyone to use this software for any purpose,
4962 including commercial applications, and to alter it and redistribute it
4963 freely, subject to the following restrictions:
4966 <item> The origin of this software must not be misrepresented; you must not
4967 claim that you wrote the original software. If you use this software
4968 in a product, an acknowledgment in the product documentation would be
4969 appreciated but is not required.
4970 <item> Altered source versions must be plainly marked as such, and must not
4971 be misrepresented as being the original software.
4972 <item> This notice may not be removed or altered from any source