Early calculating devices
| Device | Inventor / origin | Key point |
|---|---|---|
| Abacus | Ancient Asia / Mesopotamia | Earliest known counting aid using beads |
| Napier's Bones | John Napier (1617) | Numbered rods for multiplication; Napier also invented logarithms |
| Pascaline | Blaise Pascal (1642) | Mechanical adding machine (addition and subtraction) |
| Stepped Reckoner | Gottfried Leibniz (1670s) | Could also multiply and divide |
| Jacquard Loom | Joseph Marie Jacquard (1804) | Used punched cards to control weaving patterns |
| Difference Engine / Analytical Engine | Charles Babbage (1822 / 1837) | Analytical Engine had a "mill" (like ALU) and "store" (like memory); Babbage is the Father of the Computer |
| Tabulating Machine | Herman Hollerith (1890) | Punched cards for the 1890 US census; his company later became part of IBM |
| Harvard Mark I | Howard Aiken with IBM (1944) | Electro-mechanical computer |
Ada Lovelace wrote an algorithm for the Analytical Engine and is called the first computer programmer (the language Ada is named after her). Alan Turing described the Turing machine (1936) and is called the father of theoretical computer science and AI. John von Neumann proposed the stored-program concept (instructions and data in the same memory), the basis of almost every modern computer.
Early electronic computers
- ENIAC (Electronic Numerical Integrator and Computer) – built by J. Presper Eckert and John Mauchly at the University of Pennsylvania; unveiled in 1946; about 18,000 vacuum tubes; weighed around 30 tonnes.
- EDVAC – stored-program design described by von Neumann.
- UNIVAC I (1951) – early commercial computer in the USA, also by Eckert and Mauchly.
Generations of computers
| Generation | Approx. period | Technology | Languages / features | Examples |
|---|---|---|---|---|
| First | 1940s–1956 | Vacuum tubes | Machine language; punched cards; magnetic drums; huge, hot, unreliable | ENIAC, EDVAC, UNIVAC I |
| Second | 1956–1963 | Transistors | Assembly language, early high-level languages (FORTRAN, COBOL); magnetic core memory | IBM 1401, IBM 7094 |
| Third | 1964–1971 | Integrated Circuits (ICs) | Keyboards, monitors, operating systems, multiprogramming; BASIC, Pascal | IBM System/360 |
| Fourth | 1971–present | Microprocessors (VLSI) | Personal computers, GUI, networking, Internet; C, C++ | Intel 4004-based systems, IBM PC, Apple Macintosh |
| Fifth | Present and beyond | ULSI, parallel processing, AI | Natural language processing, robotics, expert systems, quantum computing research | AI assistants, supercomputers |
Different textbooks give slightly different year ranges; what exams test is the technology of each generation.
Key inventions
- Transistor – invented in 1947 at Bell Laboratories by John Bardeen, Walter Brattain and William Shockley (Nobel Prize 1956).
- Integrated Circuit – Jack Kilby (Texas Instruments, 1958) and Robert Noyce (Fairchild) independently.
- Microprocessor – Intel 4004 (1971), the first commercially available single-chip CPU (4-bit). Intel 8086 (1978) started the x86 family.
- Mouse – Douglas Engelbart (1960s).
- World Wide Web – Tim Berners-Lee at CERN (1989).
Computers in India
- PARAM 8000 (1991) – India's first supercomputer, developed by C-DAC, Pune, under Dr Vijay Bhatkar.
- The PARAM series continues under the National Supercomputing Mission.
- C-DAC = Centre for Development of Advanced Computing.
Generation-wise quick memory
- Vacuum tube – "Valve"
- Transistor
- IC
- Microprocessor / VLSI
- Artificial Intelligence / ULSI
Each generation made computers smaller, faster, cheaper, more reliable and less power-hungry. Heat output fell sharply from first to second generation because transistors replaced glowing vacuum tubes.
Exam tip: "Mark I" is Howard Aiken, "Analytical Engine" is Babbage, "first programmer" is Ada Lovelace, "stored program" is von Neumann. Do not mix these four.