Sinclair ZX80 / ZX81 / Z88 Forums

COPY can't be use on a compressed D_file !
And SCROLL can't be use with a COPY command.

XavSnap wrote: ↑Sat Dec 05, 2020 8:02 pm

Code: Select all

1 FOR A=0 TO 15
2 PRINT AT 20,10;"HELLO WORLD"
3 SCROLL
4 SCROLL
5 NEXT A
6 COPY

COPY can't be use on a compressed D_file !
And SCROLL can't be use with a COPY command.

Wow. Never tried it.. what would be the behavior?

Hi,
Just a printing routine bug… the COPY is based on a 16k 20x32 screen setup…
On a 1k or 2k configuration, it's the same problem.

The SCROLL routine don't rebuild the 16k memory D_File and don't fill the screen while it's process.

In case of COPY in 1k, it print the 118 character as a displayable character !


The Copy routine isn't designed to run on a 1k computer !

Thanks.. That’s good to know

Uh, I studied the copy routine and I never thought at this limit.
The ZX Printer and compatibles need a precise timing to sync the data to be outputted and the printing needle, I'm quite sure that even the tractor feed deceleration is compensated in the program loop (every 8 dot lines, thus a full text row).
I clearly remember the row/line counters(it expects full heigth), but honestly I'm not sure on how the line termination is checked.
I think it is dynamic in size, I'm quite sure LPRINT and LLIST will work with 1K.

0869 COPY LD D,+16
LD HL,+D-FILE
INC HL
JR 0876,COPY*D

16 hex=22 text lines. By the way, the collapsed D-FILE includes all the text line terminations.
I don't see the bug, in the code.. yet it's not the simpler routine

Is the collapsed D-FILE making the COPY command fail also without the SCROLL interference?