Early computers didn't have operating systems - the concept was unknown at the time. They had what we termed "monitors" which polled input devices for meaningful code. Programs were run as batch jobs, one at a time, and jobs were written in machine code or assembly language. The first machines used paper tape, punched Hollerith cards, or direct keyboard input to load memory, then a physical switch was activated to execute the program stored in memory. Think of a modern programmable calculator, without all the advanced functions - like "multiply" or "divide" - and you're getting close. Prior to the introduction of the x8086 microprocessor we had to write our own multiply and divide routines; the CPUs of the time didn't know how to do that. And quit posting multiple identical requests - it's rude and boring. "...a photo album is like Life, but flat and stuck to pages." - Shog9
