I also saw some games which are BASIC and are executed by BLOAD"CAS:", R but I don't remember which ones, and I don't know if they used the same method.
POKE&HFBB1,1 prevents CTRL+STOP.
POKE&HFF89,199 prevents to see the listing.
The Spanish "COLT36" game by Topo Soft is also made in BASIC, along with some machine code. The last BLOAD in the BASIC loader puts the program in 0x83E8. If moved (4608 bytes) from there to 0x8000, the BASIC program can be LISTed.
I looked a little COLT36. Another method is used. It initializes VARTAB as me but runs the program jumping to the address 073ACh (Main-ROM). I don't know if it is reliable and there are probably other parameters to adjust before jump to 073ACh.
The Spanish "COLT36" game by Topo Soft is also made in BASIC, along with some machine code. The last BLOAD in the BASIC loader puts the program in 0x83E8. If moved (4608 bytes) from there to 0x8000, the BASIC program can be LISTed.
Same with Cobra's Arc. At some point you could get an error and program exited to Basic.
Thanks for all the answers, they allowed me to figure out a method that doesn't involve executing a RUN command.
The easiest way I found is to set up VARTAB and TXTTAB and jump to 7E14h, which initializes a lot of things and calls a few hooks before jumping to 4601h, but since that one isn't documented, following NYYRIKKI's advice I finally decided to go with a variation of gdx's method:
NEWSTT equ 0x4601
TXTTAB equ 0xF676
VARTAB equ 0xF6C2
ARYTAB equ 0xF6C4
STREND equ 0xF6C6
DATPTR equ 0xF6C8
org 0x8000
incbin "basic.tok" ; this has the initial FF replaced with 00
start: ld hl,start
ld (VARTAB),hl
ld (ARYTAB),hl
ld (STREND),hl
ld hl,0x8001
ld (TXTTAB),hl
dec hl
ld (DATPTR),hl
jp NEWSTT
I generate the basic.tok file with my tokenizer, https://codeberg.org/pgimeno/vdptest/src/branch/master/asc2c... and to simplify the creation of a CAS file with the right start address and the BASIC program with the first byte replaced, I have created a Python program, bas2bincas.py which can be used directly in a makefile.
import sys
def main():
f = open(sys.argv[1], 'rb')
try:
bas = f.read()
finally:
f.close()
tapename = sys.argv[3]
L = len(bas) + 0x8000
stub = bytearray((0x21,L&0xFF,L>>8,0x22,0xC2,0xF6,0x22,0xC4,0xF6,0x22,0xC6,
0xF6,0x21,0x01,0x80,0x22,0x76,0xF6,0x2B,0x22,0xC8,0xF6,0xC3,0x01,0x46))
last = L + len(stub) - 1
blkmark = b'\x1F\xA6\xDE\xBA\xCC\x13\x7D\x74'
f = open(sys.argv[2], 'wb')
try:
f.write(blkmark)
f.write(b'\xD0' * 10)
f.write(('%-6s' % tapename).encode('utf8')[:6])
f.write(blkmark)
f.write(bytearray((0, 0x80, last & 0xFF, last >> 8, L & 0xFF, L >> 8)))
f.write(b'\00')
f.write(bas[1:])
f.write(stub)
# Pad CAS
f.write(b'\00' * (-(last-1) % 8))
finally:
f.close()
main()
This works fine with >=32K RAM and loading the program at start with BLOAD"CAS:",R which is the intention.
How can I simply know the exact address which I can use as the end address of my BASIC program so that I can use it in the BSAVE"BASprg",&H8000,&HmyBASprgEndAddress]?
How can I simply know the exact address which I can use as the end address of my BASIC program so that I can use it in the BSAVE"BASprg",&H8000,&HmyBASprgEndAddress]?
I tested except the Python program. Indeed NEWSTT can be used to execute a complet BASIC program without use RUN. It seems work fine. Good job Pgimeno !
Since you seem to know BASIC well, I take this opportunity to ask you for help. I can't solve the following problem. The return to Basic is done but the disk instructions become unusable.
