In many mainframe operations, known as closed shops, programmers submitted the program decks, often followed by data cards to be read by the program, to a person working behind a counter in the computer room. Many computer installations used cards with the opposite corner cut (sometimes no corner cut) as "job separators", so that an operator could stack several job decks in the card reader at the same time and be able to quickly separate the decks manually when he removed them from the stacker.

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  • In many mainframe operations, known as closed shops, programmers submitted the program decks, often followed by data cards to be read by the program, to a person working behind a counter in the computer room. Many computer installations used cards with the opposite corner cut (sometimes no corner cut) as "job separators", so that an operator could stack several job decks in the card reader at the same time and be able to quickly separate the decks manually when he removed them from the stacker. These cards (e.g. , a JCL "JOB" card to start a new job) were often prepunched in large quantities in advance. This was especially useful when the main computer did not read the cards directly, but instead read their images from magnetic tape that was prepared offline by smaller computers such as the IBM 1401. After running it, the computer operator would return the card deck and any hardcopy printed output, typically to one of a set of alphabetically-labelled cubby holes, based on the programmer's last initial. Overnight and 24 hour turnaround times were not uncommon; however, on a lightly-used system, it was possible to make make alterations and rerun a program in a few of minutes. Between these extremes it was common to stand in line waiting to submit a deck. Dedicated programmers might stay up all hours to get a few quick turnarounds. Using this expensive equipment—mainframe computer usage was measured in seconds per job — was often charged to a user's account. Other operations, such as those using smaller computers like the IBM 650, 1620 and 1130, were run as an open shop, where programmers had use of the computer for a block of time. A keypunch was usually located nearby for quick corrections. This was all batch-mode processing, as opposed to interactive processing.
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  • In many mainframe operations, known as closed shops, programmers submitted the program decks, often followed by data cards to be read by the program, to a person working behind a counter in the computer room. Many computer installations used cards with the opposite corner cut (sometimes no corner cut) as "job separators", so that an operator could stack several job decks in the card reader at the same time and be able to quickly separate the decks manually when he removed them from the stacker.
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  • Computer programming in the punch card era
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