Running code from the display file

[R-Tape]

The only program I know that runs code from the screen is Woody's splendid Scumball 2. The entire program is in the bottom segment of the display file:



I want to do something similar. Scumball2 works in SPIN, Spectaculator, QAOP and on the Next. Can anyone think of any reason why this will not run correctly on any model of Spectrum, emulator or online emulator?

[ketmar]

it's perfectly ok. just don't create interrupt table there, and remember that your code will be contended. otherwise, screen memory is just a normal memory. ;-)

[+3code]

Scumball2 works in SPIN, Spectaculator, QAOP and on the Next. Can anyone think of any reason why this will not run correctly on any model of Spectrum, emulator or online emulator?

In FUSE it runs OK.

[Lethargeek]

The only program I know that runs code from the screen is Woody's splendid Scumball 2. The entire program is in the bottom segment of the display file:

Maybe this is "the only (complete and complex) program that runs entirely in the screen memory" but definitely not the only one that sometimes runs some code in the screen memory. One of the recent examples is Redshift running decompression routine in the temporarily inactive screen page. Also some games keep code and data in the hidden screen memory permanently (sometimes in the page 5).

[ketmar]

the great TF-COPY has "maximum memory" mode, where it keeps most of its code in screen$ too.

[R-Tape]

Cheers all. It looks like this is safe to do without confusing any emulators.

Maybe this is "the only (complete and complex) program that runs entirely in the screen memory" but definitely not the only one that sometimes runs some code in the screen memory. One of the recent examples is Redshift running decompression routine in the temporarily inactive screen page. Also some games keep code and data in the hidden screen memory permanently (sometimes in the page 5).

I bet there are loads of programs that use the screen a little bit. I've often seen cracked versions where some setup code is place on the screen.

the great TF-COPY has "maximum memory" mode, where it keeps most of its code in screen$ too.

Cool. There's about 1K of code around 24000, but the whole top screen segment is being used.

[AndyC]

Didn't 007 Disassembler also run entirely from within screen RAM?