1959

IBM 1401

The IBM 1401 was IBM’s second-generation computer. Built from transistors and designed primarily for keeping business records, the 1401’s low cost and flexibility made it the most successful computer on the planet.

The computer could store data on both magnetic tape and disk, read punch cards at the astounding rate of 800 per minute, punch new cards at 250 per minute, and print 600 lines per minute on a “chain printer” that had just 26 upper-case letters, 10 numbers, and 12 special characters (&, . ¤ - $ * / % # @ ≠).

The 1401 was programmed in Autocode, or in IBM’s Symbolic Programming System, which today we would call an assembler. To avoid binary rounding errors, the system worked with decimal numbers. The 8-bit memory used 6 bits for encoding a number or letter, a parity check bit (for detecting hardware errors), and an 8th bit that marked the end of a number or text. “No space is wasted by filling in fixed-length words,” boasted the model’s manual, written at a time when every bit was precious.

The 1401’s processor consisted of individual printed circuit boards, also called cards, that each contained a few transistors and other discrete components. Systems could be purchased with 1,400, 2,000, 4,000, 8,000, 12,000, or 16,000 characters of 8-bit core storage. The small configurations were particularly attractive: small businesses could easily computerize by renting a 1401 for just $2,500 per month. (For comparison, IBM’s 701 business computer had rented for $15,000 per month in 1953.) Large organizations that already had a mainframe could rent a 1401 to transfer data from slower-speed punch cards to tape, feed the tape into the mainframe, perform their calculations, transfer the results back to tape, and use the 1401 to print the results.

The 1401 was a runaway success. By the end of 1961, there were more than 2,000 systems installed in the United States, representing a quarter of all installed computers. By the time IBM was ready to replace the 1401 with the radically different System/360 line, one-third of the computers on the planet would be IBM 1401s.

SEE ALSO IBM System/360 (1964)

IBM engineers Chester Siminitz and C. Fred Woidt review data on the IBM 1401 computer equipped with the IBM 1009 data transmission unit, which converts binary-coded decimal signals from the computer into a special transmission code.