larry (07/15/82)
Can anybody explain why interupts are so ignored in cp/m-type systems? Here at the Labs, I have often had to explain to people that MOST cpm systems do not have interupts, that i/o is done by polling. I have an idea why this is this way -- in the "early days" (when the Altair first came out) most people ran Altair BASIC [pre-Microsoft BASIC]. This BASIC was ORG'ed at zero, so the restart locations weren't available. The BASIC was also operating system independent -- there was NO operting system as there is now with cpm, so the BASIC did all the i/o console, and cassette tape (did it do the disk too?). In anycase, since it did polled i/o, that seemed to set the stage for the rest of the "world". Anybody else have any ideas? Larry Marek Bell Labs Naperville, Il.