Mixsonian


Computer Time on the Mainframe

The concept of "computer time" was an interesting thing in those days. To use the computer, the "mainframe" you had to have an account that had so many dollars allocated to it. It was "funny money" in the sense that you didn't really have to pay for it but the mainframe, being a scarce resource, they had to control access to it. Each time you ran a program the resulting printout would have a entire page detailing the costs, so much per card read, so much for computer cycles, so much for memory used, so much for each printed page of output, so much for disk or tape use and so on. For the free computer course we would get an account with $20. A typical computer run for the course might cost 50 to 80 cents. That is of course if it ran properly. If you made a mistake and put the program in a loop you could easily burn up all $20 in a single run. To prevent that you would punch on the "Job Control Card" limits for the program; max number of CPU, max pages output and max number of punch cards.

Example Control Punch Card
Punch Card