How did computers change between 1946 and the 1980's?

On February 14, 1946 at University of Pennsilvania, John Mauchly and J. Presper Eckert unveiled ENIAC, that ocuppied 1,000 square feet, weighed 30 tons and, used about 18,000 vacuum tubes. Thirty five years later, on August 12, 1981 IBM  announced the first IBM PC, formally known as the IBM Model 5150, was based on a 4.77 MHz Intel 8088 microprocessor and used Microsoft´s MS-DOS operating system. IBM revolutionized business computing and this computer was immediately successful, because it was advertised as a personal computer for everybody, because it was small and affordable for medium-income families.