The program code and data is located in low memory. The heap is located
between the program code and the stack. The default size for the parameter
-stack is 2K, you may change this by declaring an externally visible variable
-named named _stksize that holds the new stack size:
-
- unsigned _stksize = 4*1024; /* Use 4K stack */
+stack is 2K, you may change this for most platforms in the linker
+configuration.
Note: The size of the stack is only needed if you use the heap, or if you
call the stack checking routine (_stkcheck) from somewhere in your program.
lda _i ; get 'i', low byte
ldx _i+1 ; get 'i', hi byte
jsr pushax ; push it
- lda _c ; get 'c'
+ lda _c ; get 'c'
jsr pusha ; push it
jsr _baz ; call the function
sta _i ; store the result
Systems:
--------
-Supported systems at this time are: C64, C128, Plus/4, CBM 600/700, the newer
-PET machines (not 2001), Atari 8bit, and the Apple ][ (thanks to Kevin Ruland,
-who did the port).
+Supported systems at this time are: C64, C128, Plus/4, CBM 500, CBM 600/700,
+the newer PET machines (not 2001), Atari 8bit, and the Apple ][ (thanks to
+Kevin Ruland, who did the port).
+
+C16: Works with unexpanded or memory expanded C16 and C116 machines.
+ However, a maximum of 32KB from the total memory is used. The Plus/4
+ target supports up to 64K of memory, but has a small code overhead
+ because of the banking routines involved. Apart from this additional
+ overhead, the Plus/4 target and the C16 target are the same. 16K
+ machines (unexpanded C16) have 12K of memory for C programs available,
+ machines with 32K or more have 28K available. The actual amount of
+ memory is auto detected.
C64: The program runs in a memory configuration, where only the kernal ROM
is enabled. The text screen is expected at the usual place ($400), so
is enabled. This means, there are 41K of memory available to the
program.
-Plus/4: Unfortunately, the Plus/4 is not able to disable only part of it's
- ROM, it's an all or nothing approach. So, on the Plus/4, the program
- has only 28K available (16K machines are detected and the amount of
- free memory is reduced to 12K).
+Plus/4: Works with bank switching so 59K of memory are available to the
+ program.
+
+CBM 500:
+ The C program runs in bank #0 and has a total of 48K memory available.
+ This is less than what is available on its bigger brothers (CBM
+ 600/700) because the character data and video RAM is placed in the
+ execution bank (#0) to allow the use of sprites.
CBM 600/700:
The C program runs in a separate segment and has almost full 64K of
$8000, so on a 8032 or similar machine, 31K of memory are available to
the program.
-APPLE2: The program starts at $800, end of RAM is $8E00, so 33.5K of memory
- (including stack) are available.
+Apple ][:
+ The program starts at $803, end of RAM is $95FF, so 35.5K of memory
+ (including stack) are available to the program.
Atari: The startup code will adjust the upper memory limit to the installed
- memory, considering future graphics memory usage (which is allocated
- at top of RAM). The programmer can specify which graphics mode is
- about to be used by defining a variable _graphmode_used, unsigned
- char, to the mode value (mode values like Atari DOS, 0-31).
- (Please note that graphics mode selection isn't supported in the
- Atari runtime lib yet!)
- In the default case the upper memory limit will be $8035 (with Basic
- cartridge) and $A035 (without cartridge). This is the default which
- leaves room for the biggest possible graphics mode. If only standard
- text mode is used (_graphmode_used = 0), the values are $9C1F (with
- Basic) and $BC1F (no cartridge).
- The program starts at $1F00 (to leave room for DOS), and the free
- memory values are $6135 (24K, Basic, default mode), $8135 (32K, no
- Basic, default mode), $7D1F (31K, Basic, mode 0) and $9D1F (39K,
- no Basic, mode 0).
- These values are for a 48K or 64K machine.
+ memory detected at runtime. The programmer can adjust the upper memory
+ limit by setting the __RESERVED_MEMORY__ variable at link time. The
+ given __RESERVED_MEMORY__ value will be subtracted from the upper
+ memory limit used by the runtine. This memory could be used as graphics
+ memory, for example.
+ In the default case (no setting of __RESERVED_MEMORY__) the upper
+ memory limit is $9C1F (with Basic cartridge) and $BC1F (without
+ cartridge). The program starts at $2E00 by default.
+ These values are for a 48K or 64K machine.
Note: The above numbers do not mean that the remaining memory is unusable.
However, it is not linear memory and must be accessed by other, nonportable
Example, insert a break instruction into the code:
- asm ("\t.byte\t$00")
-
-Note: The \t in the string is replaced by the tab character, as in all other
-strings.
+ asm ("brk")
Beware: Be careful when inserting inline code since this may collide with
the work of the optimizer.
This feature is useful with inline assembly and macros. For example, a macro
that reads a CRTC register may be written like this:
-#define wr(idx) (__AX__=(idx), \
- asm("\tsta\t$2000\n\tlda\t$2000\n\tldx\t#$00"), \
+#define wr(idx) (__AX__=(idx), \
+ asm ("sta $2000"), \
+ asm ("lda $2000"), \
+ asm ("ldx #$00"), \
__AX__)
projects / cc65 / blobdiff