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
50K of memory are available to the program.
free memory is reduced to 12K).
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
+ 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.
(including stack) are available.
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