The first commercial computers, in the 1950s, were extremely slow and expensive by today’s standards, so it was important to keep them busy doing productive work at all times. In those days, programmers punched their programs into decks of cards like the one shown above, and passed them to operators who either fed the cards directly into the computer or copied them onto magnetic tape for input to the computer. To keep the computer busy, the operators made a job queue – placing the decks for several programs in the card reader or onto a tape. A master program called the operating system monitored the progress of the application program that was running on the computer. As soon as one application program ended, the operating system loaded and executed the next one.
Batch processing kept the computers busy at all times, but wasted a lot of human time. If a programmer made a small error in a program and submitted the job, it was typically several hours before he or she got the resultant error message back. Computer operators also had to be paid. Finally, professional keypunch operators did data entry using machines with typewriter-like keyboards that punched holes in the cards. This tradeoff of human for computer time reflected the fact that computers were extremely expensive.
- 1306 reads
