While employed at the university computing center, I had an opportunity to visit the university’s program library.
In the days of punch cards and mag tapes, a program library was not a THING, but instead it was a PLACE. In this case it was a locked room with several large cabinets with long sliding drawers. It reminded me of a morgue. On each sliding drawer was a tray with punch cards. On the front of each tray was the name of the program, generally encoded. A payroll program, for instance, might be called PR0201.
The programs in the program library were the source code, typically written in COBOL. When a change was needed to a program, a programmer would check out the source code; a clerk would go to the program library, remove the card deck, and take it to the programmer’s office. The programmer would go to one of the rooms with a key punch machine, punch new lines of the program, and insert them into the correct places in the deck.
The programmer would then bring the deck to the operations counter and submit it for compiling. One of us operators would take the deck into the computer room and run it all through the card reader. Our card reader was very high speed, something like 300-500 cards per minute.
Once all the cards were read in, the batch job would begin. The compiler would compile the program and prepare a report. If there was a compiler error, the report would indicate the approximate locations of the error.
Once successfuly compiled and tested, the binary would be transferred to one of the disk packs where compiled business programs resided. And the source code would be checked in to the program library.
Nibbles and Bauds 