CALDIC (the California Digital Computer) is an electronic digital computer built with the assistance of the Office of Naval Research at the University of California, Berkeley between 1951 and 1955 to assist and enhance research being conducted at the university with a platform for high-speed computing.

CALDIC was designed to be constructed at a low cost and simple to operate, by standards of the time, note that in a pre-1965 context there is no interactive user IO or human readable output in printed characters in most computers. There is no human readable user interface. It was a serial decimal machine with an 8-inch-diameter (200 mm), 10,000-word magnetic drum memory. (As CALDIC's decimal words were 10 digits each, the magnetic memory could store about 400,000 bits.) It contained 1,300 vacuum tubes, 1,000 crystal diodes, 100 magnetic elements (for the recording heads), and 12 relays (in the power supply). It weighed about 1,500 pounds (680 kg).^[1] It was capable of speeds of 50 iterations per second. CALDIC was a stored program computer with a six-digit instruction format (two digits for the opcode and four digits for the memory address).

The computer was initially planned by Paul Morton, Leland Cunningham, and Dick Lehmer; the latter two had been involved with the ENIAC at the University of Pennsylvania, and Lehmer had given one of the Moore School Lectures. Morton oversaw the design and construction with a team comprising electrical engineering graduate and undergraduate students at the university, more than 35 in total, including Doug Engelbart (who later invented the computer mouse) and Al Hoagland (a pioneer of the computer disk industry).

The machine was first ready for use in the summer of 1953^[2] and mostly operational in 1954.^{[citation needed]} Development cost through July 1955 was approximately $150,000.