<P> Early in 1952, a high - speed shifter was added, which improved the speed for shifting by a factor of five . In July 1953, a 100 - word expansion core memory was added to the system, using binary coded decimal, excess - 3 number representation . To support this expansion memory, ENIAC was equipped with a new Function Table selector, a memory address selector, pulse - shaping circuits, and three new orders were added to the programming mechanism . </P> <P> Mechanical and electrical computing machines have been around since the 19th century, but the 1930s and 1940s are considered the beginning of the modern computer era . </P> <P> ENIAC was, like the Z3 and Harvard Mark I, able to run an arbitrary sequence of mathematical operations, but did not read them from a tape . Like the Colossus, it was programmed by plugboard and switches . ENIAC combined full, Turing complete programmability with electronic speed . The Atanasoff--Berry Computer (ABC), ENIAC, and Colossus all used thermionic valves (vacuum tubes). ENIAC's registers performed decimal arithmetic, rather than binary arithmetic like the Z3, the ABC and Colossus . </P> <P> Like the Colossus, ENIAC required rewiring to reprogram until September 1948 . Three months earlier, in June 1948, the Manchester Small - Scale Experimental Machine (SSEM) ran its first program and earned the distinction of first stored - program computer . Though the idea of a stored - program computer with combined memory for program and data was conceived during the development of ENIAC, it was not initially implemented in ENIAC because World War II priorities required the machine to be completed quickly, and ENIAC's 20 storage locations would be too small to hold data and programs . </P>

Which was the first computer of the world