Hi, I'm going through "Spectrum Machine Language for Begginers" And its going fairly well but at the beginning I was baffled by the line "don't forget that the function of "USR" is to execute a machine language subroutine", but this was the first time USR was mentioned in the book! Can someone explain what it is and why is it the value of the bc register pair at the end of running a program? I can't find anything about it with google but my guess is its a subroutine stored in ROM/RAM??? that executes Machine code instructions.
Thanks
USR function
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Re: USR function
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ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
Re: USR function
Hi,
Just a keyboard trouble !
Don't type URS as U_S_R word.
If you type "U" "S" "R", this word is a variable, not a function!
10 LET USR=1
20 PRINT USR
RUN
1
30 RANDOMIZE USR =>> RANDOMZE 1
40 LET VAL=USR 32000 =>> VAL= 1 32000 (RETURN AN ERROR!)
You had to type "1" "0" "T" "CTRL+SHIFT" "L" "3" "2" "0" "0" "0" !
>> 10 RANDOMIZE USR 32000
Just a keyboard trouble !
Don't type URS as U_S_R word.
If you type "U" "S" "R", this word is a variable, not a function!
10 LET USR=1
20 PRINT USR
RUN
1
30 RANDOMIZE USR =>> RANDOMZE 1
40 LET VAL=USR 32000 =>> VAL= 1 32000 (RETURN AN ERROR!)
You had to type "1" "0" "T" "CTRL+SHIFT" "L" "3" "2" "0" "0" "0" !
>> 10 RANDOMIZE USR 32000
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