Harvard Mark I

Grace Murray Hopper, a Commodore in the Navy, designed COBOL and coined the phrase "debug" the computer. While she was working on the Mark II in 1945, a moth flew into the circuitry, causing an electrical short which halted the computer. While removing the dead moth, she said that the program would be running again after the computer had been "debugged." Today the process of removing errors from programs is still called debugging.

See the first "Computer Bug"

By the late 1930s punched-card machine techniques had become so well established and reliable that Howard Aiken, in collaboration with engineers at IBM, undertook construction of a large automatic digital computer based on standard IBM electromechanical parts. Aiken's machine, called the Harvard Mark I, handled 23-decimal-place numbers (words) and could perform all four arithmetic operations; moreover, it had special built-in programs, or subroutines, to handle logarithms and trigonometric functions. The Mark I was originally controlled from pre-punched paper tape without provision for reversal, so that automatic "transfer of control" instructions could not be programmed. Output was by card punch and electric typewriter. Although the Mark I used IBM rotating counter wheels as key components in addition to electromagnetic relays, the machine was classified as a relay computer. It was slow, requiring 3 to 5 seconds for a multiplication, but it was fully automatic and could complete long computations without human intervention. The Harvard Mark I was the first of a series of computers designed and built under Aiken's direction.