First, we keypunch our program and data cards. Keypunch operators punched cards using an IBM 026 keypunch machine. 80-column punched cards were a primary means of inputting programs and data into the computer. Each non-blank character required 1, 2, or 3 holes in a card column using the Hollerith code. The keypunch machine was not connected to the computer. Decks of punched cards had to be brought over to be read by the computer's card reader.
Examples of punched cards. Both programs and data were punched into decks of these cards. The cards were commonly called “IBM cards” since so much computing equipment and media back then were made by IBM. Before disk drives became popular, most data were stored on punched cards, and later, on magnetic tape.
Now we have our program deck. This is a very short program. Large applications could include thousands of program and data cards. Many thanks to Stan Paddock, 1401 restorer and docent, who explained and demonstrated the data processing equipment.
Into the card reader they go. Each card sweeps past an assembly of 80 wire brushes, one per card column. The wires go through the holes to complete an electrical circuit, thereby sending the contents of each card to the computer. The IBM 1402 card reader can read up to 800 cards per minute.
Don't ignore the flashing front panel lights! The IBM 1401 computer system has a transistor-based 87 KHz CPU. The main unit includes 4,000 memory locations, and an additional 12,000 memory locations are housed in a separate unit, for a grand total of 16,000 8-bit locations. The computer uses non-volatile core memory. Programmers back then really knew how to squeeze their programs into very little memory using techniques such as segmentation and overlays.
Mounting magnetic tape. Each 2400' reel of 7-track magnetic tape can store around 3 MB of data, depending on the block size and blocking factor. The IBM 729 tape drive has a 480 K bits/second transfer rate. The tape is looped through the two vertical vacuum columns below the two tape reels to buffer the tape physically, which enables the drive mechanism to move the tape rapidly in either direction past the read-write heads.
Finally, our printout! This IBM 1403 chain printer can print 600 lines per minute with each line up to 132 characters long. The printing mechanism consists of 132 hammers, one behind each print position, and a looped print chain containing the characters whirling in front of the inked ribbon and paper. As the correct character passes by each print position, the hammer fires and strikes the paper and the ribbon against the print chain. No, the print chain does not stop for each character! Computer equipment back then were not only electronic marvels, but electromechanical as well.
