ENIAC was the first general-purpose electronic digital computer, financed by the U.S. Army and built during World War II at the University of Pennsylvania to calculate artillery firing tables. It was 1000 times faster than any previous machine but difficult to reprogram. EDVAC was an improved stored-program computer designed by the ENIAC team to be easier to program by storing programs in memory; it pioneered the modern computer architecture of stored programs. EDVAC was completed in 1949 and in continuous operation until 1961, proving reliable and productive during its lifetime.

1. • ENIAC, short for Electronic Numerical Integrator And
Computer, was the first general-purpose, electronic
computer. It was a Turing-complete, digital computer
capable of being reprogrammed to solve a full range
of computing problems.
• ENIAC was conceived and designed by John Mauchly
and J. Presper Eckert of the University of
Pennsylvania.

2. • The ENIAC's design and construction was financed by the United States Army during World
War II. The construction work started secretly by the University of Pennsylvania's Moore
School of Electrical Engineering in July 1943 under the code name “Project PX”. It was
completed in February 1946 and had cost 500,000 $. It was put to use in the army in July
1946 and was shut down in November 1946 for memory upgrade and refurbishment. It was
turned back on in July 1947 and was in continuous operation until 11:45 p.m. on October 2,
1955.
• The ENIAC contained 17,468 vacuum tubes, along with 70,000 resistors, 10,000 capacitors,
1,500 relays, 6,000 manual switches and 5 million soldered joints. It covered 1800 square feet
(167 square meters) of floor space, weighed 30 tons, and consumed 160 kilowatts of
electrical power.
• ENIAC was one thousand times faster than any other calculating machine to date. In one
second, the ENIAC could perform 5,000 additions, 357 multiplications or 38 divisions. The use
of vacuum tubes instead of switches and relays created the increase in speed, but it was not
a quick machine to re-program. Programming changes would take the technician’s weeks,
and the machine always required long hours of maintenance.
• As a side note, research on the ENIAC led to many improvements in the vacuum tube.

3. EDVAC
• EDVAC short for Electronic Discrete Variable Automatic Computer, was one of the
earliest electronic computers. Unlike its predecessor the ENIAC, it was binary
rather than decimal, and was a stored program machine.
• ENIAC‘s designers wanted to eliminate the intolerable fact that reprogramming the
computer required a physical modification of all the patch cords and switches. It
took days to change ENIAC's program.
• John Mauchly and J. Presper Eckert teamed up with the mathematician John von
Neumann to design EDVAC, which pioneered the stored program. They proposed
the EDVAC's construction in August 1944, and design work for the EDVAC
commenced 2 years before the ENIAC was fully operational.
• The design would implement a number of important architectural and logical
improvements conceived during the ENIAC's construction and would incorporate a
high speed serial access memory. Like the ENIAC, the EDVAC was built for the U.S.
Army's Ballistics Research Laboratory at the Aberdeen Proving Ground by the
University of Pennsylvania's Moore School of Electrical Engineering.
• A contract to build the new computer was signed in April 1946 with an initial
budget of US $ 100,000. The contract named the device the Electronic Discrete
Variable Automatic Calculator. The final cost of EDVAC, however, was similar to the
ENIAC's, at just under US $ 500,000.

4. • The EDVAC was a binary serial computer with automatic addition, subtraction, multiplication,
programmed division and automatic checking with an ultrasonic serial memory capacity of 1,000
44-bit words which was later set to 1,024 words, thus giving a memory, in modern terms, of 5.5
kilobytes.
• Physically, the computer contained a magnetic tape reader-recorder, a control unit with an
oscilloscope, a dispatcher unit to receive instructions from the control and memory and direct
them to other units, a computational unit to perform arithmetic operations on a pair of numbers at
a time and send the result to memory after checking on a duplicate unit, a timer, a dual memory
unit consisting of two sets of 64 mercury acoustic delay lines of eight words capacity on each line,
and three temporary tanks each holding a single word.
• The computer had almost 6,000 vacuum tubes and 12,000 diodes, and consumed 56 kW of power.
It covered 490 ft² (45.5 m²) of floor space and weighed 17,300 lbs. (7,850 kg). The full complement
of operating personnel was thirty people for each eight-hour shift.
• EDVAC's addition time was 864 microseconds and its multiplication time was 2900 microseconds
(2.9 milliseconds).
• EDVAC was delivered to the Ballistics Research Laboratory in August 1949. After a number of
problems had been discovered and solved, the computer began operation in 1951 although only on
a limited basis. Its completion was delayed because of a dispute over patent rights between Eckert
and Mauchly and the University of Pennsylvania, resulting in Eckert and Mauchly's resignation and
departure to form the Eckert-Mauchly Computer Corporation and taking most of the senior
engineers with them.
• By 1960 EDVAC was running over 20 hours a day with error-free run time averaging eight hours.
EDVAC received a number of upgrades including punch-card I/O in 1953, extra memory in slower
magnetic drum form in 1954, and a floating point arithmetic unit in 1958.
• EDVAC ran until 1961 when it was replaced by BRLESC. During its operational life it proved to be
reliable and productive for its time.