How computers evolved

Computing has a long history:

• The abacus, a frame of beads, was used for simple arithmetic thousands of years ago.
• Blaise Pascal's Pascaline (1642) was a mechanical calculator that could add and subtract directly.
• Charles Babbage's analytical engine (1834) was designed to input, process, store and display output: the basic plan of every modern computer. It was mechanical, not electronic.
• Herman Hollerith's tabulating machine (1890) summarised data stored on punched cards; it was used for the US census.

The modern computer took shape in the twentieth century:

• Alan Turing's machine (1937) described a general purpose, programmable machine.
• John Von Neumann's stored-program idea: keep both the program and its data in the computer's memory. Almost all computers still work this way.
• Transistors (1947) replaced bulky, hot vacuum tubes.
• Integrated circuits (around 1970) put many transistors on one chip, making computers much smaller.

Gordon Moore predicted in 1965 that the number of transistors on a chip would double about every two years (Moore's Law). It held true for decades. LSI (large scale integration) put a whole CPU on a single chip, the microprocessor; VLSI in the 1980s put about 3 million components on one chip.

Computers then reached everyone. IBM's personal computer arrived in 1981, and Apple's Macintosh in 1984. Operating systems with a graphical user interface (icons and windows) and the World Wide Web (1990s) made computers easy for anyone. Then came laptops, smartphones, tablets and wearable gadgets, and everyday smart appliances joined the Internet of Things.