Pariksha SaathiLesson 1 of 10 · Computer Knowledge
Computer Fundamentals: History, Generations and Types of Computers
Drafted with AI assistance and fact-checked on 28 October 2026; not yet read line by line by a human editor. Spotted a mistake? Tell us. Editorial standards & corrections
What a computer is
A computer is an electronic device that accepts data as input, processes it according to a stored set of instructions called a program, stores the data and results, and gives output as useful information. The word comes from the Latin computare, to calculate. Raw facts are data; processed, meaningful data is information. Every computer follows the input-process-output cycle, with storage supporting each step. A computer has no intelligence of its own and does exactly what the program says, so the rule GIGO (garbage in, garbage out) applies: wrong input gives wrong output.
Characteristics
Exams list speed (work is measured in microseconds, nanoseconds and picoseconds), accuracy (errors come from wrong data or programs, not from the machine), diligence (it never tires, so the millionth calculation is as accurate as the first), versatility (the same machine types letters, calculates salaries and plays music), storage (it holds huge amounts of data and recalls it instantly) and automation (a program, once started, runs without human help). Its limitation is that it cannot think, feel or decide on its own.
Before electronics
The abacus, a frame of sliding beads long used in China, is regarded as the earliest calculating device. John Napier devised Napier's Bones in 1617 for multiplication. Blaise Pascal built the Pascaline in 1642, often called the first mechanical adding machine, which could add and subtract; Gottfried Leibniz's machine of the 1670s could also multiply and divide. Joseph Marie Jacquard's loom of the early 1800s used punched cards to control weaving, an idea later used for computer input. Charles Babbage designed the Difference Engine in 1822 and then the Analytical Engine, which had a mill (processor), a store (memory) and punched-card input; this is why he is called the Father of the Computer. Ada Lovelace wrote a method for computing numbers on it in 1843 and is called the first programmer. Herman Hollerith's punched-card tabulator processed the 1890 US Census, and his company later became part of IBM.
The electronic age
Alan Turing described the theoretical Turing machine in 1936. The Harvard Mark I (1944) of Howard Aiken was electromechanical. ENIAC (Electronic Numerical Integrator and Computer), built by J. Presper Eckert and John Mauchly at the University of Pennsylvania and unveiled in 1946, was the first general-purpose electronic digital computer; it used about 18,000 vacuum tubes and weighed about 30 tons. John von Neumann's stored-program concept, keeping the program in memory along with the data, shaped EDVAC and nearly every later computer. UNIVAC I (Universal Automatic Computer), also by Eckert and Mauchly, was delivered to the US Census Bureau in 1951 as the first commercial computer made in the United States.
Five generations
Each generation is named after its main electronic component; books differ slightly on the years, but not on the technology. First (about 1946-1959): vacuum tubes, machine language, magnetic drum memory, great size and heat; ENIAC, EDVAC and UNIVAC I. Second (about 1959-1965): transistors, invented at Bell Labs in 1947; assembly language and the first high-level languages FORTRAN and COBOL; magnetic core memory; the IBM 1401. Third (about 1965-1971): integrated circuits, invented by Jack Kilby in 1958 and independently by Robert Noyce; keyboards, monitors and operating systems; the IBM System/360. Fourth (1971 onwards): the microprocessor, built with LSI and then VLSI chips, starting with the Intel 4004 in 1971; personal computers such as the IBM PC of 1981, graphical interfaces and networks. Fifth (present and future): ULSI, parallel processing and artificial intelligence.
Types of computers
By the data they handle, computers are analog (they measure continuous quantities such as temperature, speed or voltage, like a speedometer), digital (they work on discrete values, ultimately 0 and 1, like a PC or a calculator) and hybrid (both together, like ICU patient monitors or a petrol pump dispenser). By purpose they are general-purpose or special-purpose (embedded in washing machines, ATMs and traffic signals). By size, supercomputers are the fastest, rated in FLOPS (floating-point operations per second) and used for weather forecasting and nuclear simulation; the CRAY-1 (1976) of Seymour Cray, the father of supercomputing, is the classic example. Mainframes serve thousands of users at once in banks and railway reservation. Minicomputers are mid-range multi-user machines. Microcomputers, built around one microprocessor, include desktops, laptops, tablets and smartphones.
India's firsts
India's first digital computer, the HEC-2M, imported from Britain, was installed at the Indian Statistical Institute (ISI), Kolkata, in 1956 (some accounts say 1955). TIFRAC, the first digital computer designed and built in India, was commissioned at the Tata Institute of Fundamental Research, Mumbai, in 1960, and ISIJU, built by ISI with Jadavpur University in the mid-1960s, was the first transistorised computer built in India. After the United States refused to export a Cray supercomputer, the government set up C-DAC (Centre for Development of Advanced Computing) in Pune in 1988; under Vijay Bhatkar it built PARAM 8000, India's first supercomputer, in 1991.
Key facts
- Blaise Pascal's Pascaline (1642) is often called the first mechanical adding machine; it could only add and subtract.
- Charles Babbage, the Father of the Computer, designed the Difference Engine (1822) and the Analytical Engine, which had a mill, a store and punched-card input; Ada Lovelace is called the first programmer.
- ENIAC (1946, Eckert and Mauchly, University of Pennsylvania) was the first general-purpose electronic digital computer, with about 18,000 vacuum tubes.
- UNIVAC I (1951) was the first commercial computer made in the US; its first customer was the US Census Bureau.
- Generations by technology: vacuum tubes, transistors, integrated circuits, microprocessors (VLSI), then ULSI and artificial intelligence.
- The Intel 4004 (1971) was the first commercial microprocessor and marks the start of the fourth generation.
- Analog computers measure continuous quantities (speedometer); digital computers work on discrete 0s and 1s; hybrid computers such as ICU monitors combine both.
- Supercomputer speed is measured in FLOPS; Seymour Cray, builder of the CRAY-1 (1976), is called the father of supercomputing.
- HEC-2M at ISI Kolkata (1956) was India's first digital computer; TIFRAC (1960) the first digital computer built in India; PARAM 8000 (1991, C-DAC Pune, Vijay Bhatkar) India's first supercomputer.
- GIGO means garbage in, garbage out: a computer's output is only as good as its input and its program.
Quick revision
Computer: input-process-output, from Latin computare; Pascaline 1642 (add, subtract); Babbage: Difference Engine 1822, Analytical Engine, Father of the Computer; Ada Lovelace first programmer; ENIAC 1946 (about 18,000 vacuum tubes); UNIVAC I 1951 first US commercial computer; generations: vacuum tube, transistor, IC, microprocessor, AI/ULSI; analog, digital, hybrid; super, mainframe, mini, micro; HEC-2M 1956; TIFRAC 1960; PARAM 8000 1991.