Re: A86: Interrupts vs. SQRT and ANS
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Re: A86: Interrupts vs. SQRT and ANS
In a message dated 2/27/99 4:45:41 PM Eastern Standard Time, ahmed@ticalc.org
writes:
> Would someone tell me the major difference.. I thought they were the
> same thing, but I heard from Kirk that you can't change variables from an
> interrupt but you can from a SQRT.. and also, what are the calls for
> modifying "ans?" thanks!
the interrupt runs at 200hz and starts at $38. you can install your own im 1
interrupt addon (limited to 200 bytes), or your own im 2 routine, which is
probably the better choice. from an interrupt, you don't really have direct
access to any specific thing in the way you do in a sqrt. however, i'm pretty
sure that you can modifty variables and write to the screen and just about
anything else you want from an interrupt. unless di is executed, an interrupt
is constantly running.
a sqrt is a program which is executed when a specific event is called.
probably the most common is the sqrt key program, which runs every time
_getkey is called. from that, you can very easily modify all keypresses
handled by the system. other sqrt key programs (that i can think of off the
top of my head) are: sqrt form, sqrt graph, sqrt exec, sqrt parse, and maybe a
couple others.
a sqrt program is optimized for handling specific calculator events, whereas
an interrupt is run 200 times a second, regardless of what else is going on.
hope this clears things up.
btw, didn't you quit z80 programming?