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The UNIVAC I (UNIVersal Automatic Computer I) was the first commercial computer made in the United States. It was designed by J. Presper Eckert and John Mauchly, the men behind the first electronic computer, the ENIAC. During the years before successor models of the UNIVAC I appeared, the machine was simply known as "the UNIVAC".

The first UNIVAC was delivered to the United States Census Bureau on March 30, 1951. The fifth (built for the Atomic Energy Commission) was used by CBS to predict the 1952 presidential election. With a sample of just 1% of the voting population it predicted that Eisenhower would win; something nobody would believe, but UNIVAC was right!

The UNIVAC I computers were built by Remington Rand's Univac-division (successor of the Eckert-Mauchly Computer Corporation (EMCC), bought by Rand in 1950).

Table of contents
1 Description
2 History
3 External links


UNIVAC I used 5,200 vacuum tubes, weighed 29,000 pounds (13 metric tons), consumed 125 kW, and could perform about 1,905 operations per second running on a 2.25 MHz clock. The mercury delay line memory unit alone was 14 feet by 8 feet by 8.5 feet high (4.3 m × 2.4 m × 2.6 m). The complete system occupied more than 350 ft² (35.5 m²) of floor space.

The main memory is 1000 words of 11 decimal digits plus sign (72 bit words), consisting of 100 channels of 10 word mercury registers. The input and output memory is 120 words, consisting of 12 channels of 10 word mercury registers. There are 6 channels of 10 word mercury registers as spares. With modified circuitry, 7 more channels control the temperature of the 7 mercury tanks, and one more channel is used for the 10 word "Y" register. The total of 126 mercury channels is contained in the 7 mercury tanks mounted on the backs of sections MT, MV, MX, NT, NV, NX, and GV. Each mercury tank is divided into 18 mercury channels.

Each 10 word mercury channel is made up of three sections:

  1. A channel in a column of mercury, with receiving and transmitting quartz crystals mounted at opposite ends.
  2. An intermediate frequency chassis, connected to the receiving crystal, containing amplifiers, detector, and compensating delay, mounted on the shell of the mercury tank.
  3. A recirculation chassis, containing cathode follower, pulse former and retimer, modulator, which drives the transmitting crystal, and input, clear, and memory-switch gates, mounted in the sections adjacent to the mercury tanks.

Instructions were 36 bits long, packed 2 per word.

Numbers were represented using excess-3 binary coded decimal arithmetic with 6 bits per digit (and one parity bit per digit for error checking), allowing 11 digit signed magnitude numbers.


As well as being the first American commercial computer, the UNIVAC I was the first computer designed at the outset for business use.

The first contracts were with government agencies, the Census Bureau, the United States Air Force, and the Army Map Service. Contracts were also signed by the A.C. Nielsen Company, and the Prudential Insurance Company.

Following the sale of Eckert-Mauchly Computer Corporation to Remington Rand, due to the cost overruns on the project, Remington Rand convinced Nielsen and Prudential to cancel their contracts. After the first three UNIVAC I systems, two were sold to the Atomic Energy Commission, and one to the United States Navy. The seventh UNIVAC I was installed at the Remington Rand sales office in New York City.

The eighth UNIVAC I, the first sale for business applications, was installed at the General Electric Appliance Division, to do payroll, in January, 1954. DuPont bought the twelfth UNIVAC I, it was delivered in September, 1954. Pacific Mutual Insurance received a UNIVAC I system in August, 1955. Other insurance companies soon followed.

The Census Bureau got a second UNIVAC I in October 1954.

Originally priced at $159,000, the UNIVAC I rose in price until they were between $1,250,000 and $1,500,000.

The UNIVAC I was too expensive for most universities, and Sperry Rand was not strong enough financially to afford to give many away. However Sperry Rand donated UNIVAC I systems to Harvard University (1956), the University of Pennsylvania (1957), and Case Institute of Technology in Cleveland, Ohio (1957).

A total of 46 UNIVAC I systems were eventually built and delivered.

External links