Modified C64 PRG BASIC header?

Question

I recently bought a c64 mini and been trying to code some assembly using Turbo Macro Pro v1.2.

While working on the hello world program I found a tutorial where an auto run BASIC header was used.

I tried to also include a PRINT CHR$(147) to clear the screen, but I get an OUT OF MEMORY ERROR.

the original BASIC header was:

*=$0801
.byte $0c, $08, $0a, $00, $9e, $20
.byte $34, $30, $39, $36, $00, $00
.byte $00

I modified it to:

*=$0801
.byte $0e, $08, $0a, $00, $99, $20
.byte $c7, $28, $31, $34, $37, $29
.byte $00, 
.byte $19, $08, $14, $00, $9e, $20
.byte $34, $30, $39, $36, $00, $00
.byte $00

When I assemble and run from TMP and then type LIST i get,

10 PRINT CHR$(147)
20 SYS 4096

But when RUN I get the OUT OF MEMORY ERROR at line 10.

Am I doing something wrong? Or is it really out of memory for this instruction?

TMP is still loaded in memory in the background. I'm currently running this in VICE.

Hostetler

It's unclear what TMP is. Is that your whole code? Do you have the load address set for your PRG? Sounds like CHR$ is trying to allocate a new string and fails because it thinks there is no free memory left. – Nerin

Sorry, TMP is Turbo Macro Pro v1.2. In the full code I have some assembly code at *=$1000. but if the BASIC line is 10 SYS 4096, I don't get the OUT OF MEMORY ERROR. – Hostetler

Turns out that if I assemble to disk and then restart and RUN from disk it works fine, so must be some memory problem with TMP. I just don't understand what. – Hostetler

Answer 1

I would guess that TMP allocates all of the memory it can for lookup tables, intermediate code etc. The last thing it wants is BASIC messing things up and so it will point the top of BASIC memory somewhere safe. Allocatable BASIC memory can be found in pointers at 43-44 and 55-56, indicating the start/end of BASIC memory. Normally, they are $0801 to $A000 but I'm guessing TMP sets them otherwise.

Adin