Anything Sinclair ZX Basic related; history, development, tips - differences between BASIC on the ZX80 and ZX81
David G
Posts: 387 Joined: Thu Jul 17, 2014 7:58 am
Location: 21 North, 156 West
Post
by David G » Sun Jul 17, 2022 1:39 am
XavSnap wrote: ↑ Thu Jul 14, 2022 3:25 pm The variable isn't set !
Before the "LET P=." the "P" value isn't set... and can't be viewed in the Vars memory room.
A PRINT P; , will give a 2/0 error report.
But, but the ROM call use a blank variable name ghosted in the Vars the keep it in memory
I am not understanding
If i enter
then enter
It prints 0 as expected
Does this not mean that the variable has been added by name ('P') to the
Variables zone of memory ? What is meant by "ghosted" name?
XavSnap
Posts: 1946 Joined: Sat May 10, 2008 4:23 pm
Location: 'Zx81 France' Fb group.
Post
by XavSnap » Sun Jul 17, 2022 3:25 am
Hi David,
Ghosted in the BASIC, not in the Vars if the LET command is not RUN.
BASIC:
VARS after a RUN
$75= "P" character + bit 6 (+64) .
Xavier ...on the Facebook groupe : "Zx81 France"(fr)
David G
Posts: 387 Joined: Thu Jul 17, 2014 7:58 am
Location: 21 North, 156 West
Post
by David G » Sun Jul 17, 2022 11:59 pm
OK, your explanation makes sense. "ghosted" = "hidden" floating-point value. In the BASIC line it is ghosted. Yes
And when the LET statement is RUN, the BASIC system copies it from there to the Variables memory area/zone/room/place
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