How old is the CPU?

Answer 1

The first thing that we would now call a Central Processing Unit (CPU) was designed in the 1830s by Charles Babbage in London. He called it the Mill. It was part of his never built Analytical Engine mechanical computer.

The first things that we would now call a Central Processing Unit (CPU) that actually were built were designed and built in the 1930s: two of these were Howard Aiken's Harvard Mark I electromechanical computer and the Atanasoff Berry Computer (ABC) electronic computer. Both of these were finished and running in 1942. Bell Labs also built their electromechanical Complex Number Calculator computers in this general time period, using a fixed point complex number Central Processing Unit (CPU).

Note: ENIAC (often incorrectly credited as the first electronic digital computer) did not have a CPU, instead it had 20 accumulators in separate panels that ran completely independently. It was designed in 1943/1944 but was not finished until November 1945.

The Manchester Small-Scale Experimental Machine (SSEM), nicknamed Baby, was the first postwar computer with a Central Processing Unit (CPU). it was finished in 1948 and was also the first computer to be programmed with instructions stored in the same memory as data (i.e. stored program).