ZX81 ‘BASIC’ peek function

Question

I want to find the code of a character printed.

This is the code:

10 Print AT 2,2; "T"
20 Let C=Peek(Peek 16398+256*Peek 16399)
30 Print Peek(C)

It should just print the Code value of T.

I could later use:

40 Print Peek (Code C)

Or something.

But the 10-30 bit doesn't work. It always returns '0' -With different letters too: G,T 'black graphic' and M,

What am I doing wrong?

Will be used for collision detection.

This is just a test to see if it works. :) Not a full program :P — James Andrew, Jul 07 '10 at 22:18
How is this different from your earlier question: http://stackoverflow.com/questions/3196853/help-zx81-basic-peek-function ? — Paul R, Jul 07 '10 at 22:39
That is a question. This is a question to a response to that question :) — James Andrew, Jul 08 '10 at 06:57
possible duplicate of [Help: ZX81 BASIC "Peek" function](http://stackoverflow.com/questions/3195111/help-zx81-basic-peek-function) — Joe, May 26 '14 at 11:47

score 1 · Answer 1 · answered Jul 07 '10 at 22:27

According to this it is the right address to peek, but maybe the cursor is not at the right position? If I remember well (man, what are you doing with that old thing :-) ! ) the PRINT AT might move the cursor one position after the printed char (or one line under).

score 1 · Accepted Answer · answered Jul 08 '10 at 09:20

jdehaan's right, printing the T without a trailing ; will move the cursor down to the next line after printing. (With ;, it's be one position to the right.)

To read the character you'd just written you'd have to move back a position again:

PRINT AT 2,2;"T";AT 2,2;
PRINT PEEK(PEEK 16398+PEEK 16399*256)

gives me 57, which is the character code for T.

ZX81 ‘BASIC’ peek function

2 Answers2