Grace Hopper and symbolic notation, making programming easier. Computers are less prone to failure. Computers are smaller. Computers are faster. Computers use less electricity.
Mass production makes computers less expensive.
Timesharing allows users at different terminals to work with the same mainframe at the same time. The most powerful mainframes are called supercomputers. The Microcomputer Revolution Began in the late 1970's with Apple, Tandy and Commodore. Personal computers are low-cost, typewriter size computers. Today's personal computers are as powerful as mainframes were before.