How computers evolved

Computing devices evolved from simple calculators to powerful data processors in a short time. Key inventions:

• Abacus (about 3,000 years ago, shown at 500 BC on the book's timeline): a mechanical device for simple arithmetic.
• Pascaline (1642): Blaise Pascal's mechanical calculator; it could add and subtract two numbers directly, and multiply and divide by repeated addition or subtraction.
• Analytical engine (1834): Charles Babbage's mechanical device for inputting, processing, storing and displaying output; seen as the basis of modern computers.
• Tabulating machine (1890): Herman Hollerith's machine to summarise data stored on punched cards (stiff paper with holes in set positions); a first step towards programming.
• Turing machine (1937): the idea of a general-purpose programmable machine able to solve any problem by running a program.
• Stored-program computer (1945): John von Neumann's idea of keeping both data and program in memory. The von Neumann architecture has a CPU, memory, input/output devices and communication channels. Early machines built on these ideas include ENIAC and EDVAC.
• Transistor (1947): developed at Bell Labs from semiconductors, it replaced vacuum tubes.
• Integrated circuit (1970 on the book's timeline): a silicon chip holding a whole electronic circuit, which shrank computers drastically.

Miniaturisation:

• In 1965, Intel co-founder Gordon Moore predicted (Moore's Law) that the number of transistors on a chip would double about every two years, while cost fell.
• In the 1970s, Large Scale Integration (LSI) put a complete CPU on one chip: the microprocessor.
• In the 1980s, Very Large Scale Integration (VLSI) put about 3 million components on a small chip; Super Large Scale Integration (SLSI) packs in even more.

Computers for everyone:

• IBM introduced its first personal computer (PC) in 1981; Apple introduced the Macintosh in 1984.
• Graphical User Interface (GUI) operating systems replaced command-line systems like UNIX and DOS, and the World Wide Web in the 1990s spread computer use further.
• Then came laptops, smartphones, tablets; now wearables (smart watches, lenses, headbands) and smart appliances in the Internet of Things (IoT), using artificial intelligence.

Example (new): a calculator watch from the 1980s and today's smartwatch are both wearable computers, but the smartwatch's chip holds many thousands of times more transistors: Moore's Law at work over four decades.