When was the computer first invented and who invented it?

It was invented in 1856 by an English fellow named Charles Babbage.

Nobody really knows when the first computer was invented.

It has many inventors that have contributed to the history of computers.

technically speaking the first computer was made in the c.3rd century A.D. it was called the abacus is consisted of of movable counters to speed up computations it is not known as to whom made the abacus but just remember that computers are counting machines and that some of the first computers were made for calculation and there for they are calculators.

Charles Babbage's Analytical Engine back in 1837 is considered to be the first computer by many experts.

There were several people whose work is noteworthy in this regard.

I recommend "Why Was the Computer Invented When It Was" by Tom Korner for a good overview on how and when the first computers were developed.

maths.org is a good reference.

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The first computer was invented by a British scientist Charles P.Babbage in 1822 but completed in 1871 by Helmet P.Babbage (the son of Charles P.Babbage).

The Difference Engine: The first of these devices was conceived in 1786 by J. H. Mueller. It was never built. Difference engines were forgotten and then rediscovered in 1822 by Charles Babbage. This machine used the decimal numbers system and was powered by cranking a handle. The British government first financed the project but then later cut off support. Babbage went on to design his much more general analytical engine but later returned and produced an improved design (his "Difference Engine No. 2") between 1847 and 1849.

You could start with Charles Babbage's Difference engine or the ABC created by John Vincent Atanasoff and Clifford Berry in 1942.

Also consider the mechanical analog computer known as the Antikythera Mechanism built ca. 100 BC it may have been created by Archimedes.