Mainframe  My interest in computers started when I emigrated to Canada. The company I worked for in Toronto had a two IBM 1401 computers and an IBM 7074 mainframe... and I got to write programmes for them. The 7074 was a magnetic tape in and magnetic tape out mainframe; it had no other input or output devices other than the typewriter console. It was the speed machine. The 1401s were much smaller and slower but each had input and output devices to read and write punched cards and magnetic tapes and one or both of them had a printer. I think the 7074 had 10K words of core memory while the 1401s had 4K and 8K. Since memory was tight, one developed the skill of writing tight code.

These machines were not multi-tasking: they ran only one job at a time. One often had to wait a week to get a programme run. In order to save expensive computer time, assembling or compiling a programme into machine language was done very rarely and the machine code saved as a deck of punched cards. If a programme bug needed fixing, it was done by hand coding machine language and adding more cards to the deck. Only when the process became unmanageable was the programme reassembled or recompiled.

One wrote programmes on an 80-column coding sheet. Again, there were many different coding sheets for different programming languages and data but all with 80 columns. After coding, the coding sheets went to the keypunch department to be converted into a deck of punched cards. This deck of cards was then sent to the computer department with a job sheet which specified what was to be done with them. For my jobs, it specified that the card deck was to be run on a 1401 to produce a magnetic tape; the tape was then to be used as input to the 7074 which would produce one or more output magnetic tapes. These tapes were to be passed to a 1401 where they would be converted into printed output. Often, instructions were given to store a magnetic tape in the Tape Library for future reuse of its data.

Later, the 7074 was replaced with an IBM 360 and there followed a whole series of mainframes in the 360 and 370 design.

The first mainframe computer language I learned and used was Fortran 2 but this was followed in the ensuing years by Fortran IV, 1401 Autocoder, 7074 Autocoder, 360 Assembler, COBOL, PL/1, Mark IV, APL and probably some others that I have forgotten.

I fell in love with programming and have been involved in it in one form or another ever since.

At right is an 80-column punch card. This is the “General Purpose” card. There were many different cards, all the same size and shape and 80 columns but with varying colours and designs to make it easier for humans to use them. For instance we used red cards for hand-coded machine code to patch bugs. The red cards were easily seen in the original deck of white cards.