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Five generations of computers

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⏱ 4 min read🧩 6 question types🎯 18 practice Q
The idea in one minute

Computers are grouped into five generations. Each generation is named after the switching part at the heart of the machine. The order is vacuum tube, transistor, integrated circuit (IC), microprocessor, then artificial intelligence. Learn this ladder once and most questions answer themselves.

01

What a generation means

A generation is one stage in the history of computers. Each stage is named after its switching part. This part works like tiny on/off switches inside the machine.

When the switching part changed, computers became smaller, faster, cheaper and cooler. Exams ask which technology, which machine or which feature belongs to which generation.

GenerationPeriodCore technologyExample machines
First1940-1956Vacuum tubesENIAC, EDVAC, EDSAC, UNIVAC-I, IBM 701
Second1956-1963TransistorsIBM 1401, IBM 7094
Third1964-1971Integrated Circuits (ICs)IBM 360, PDP-8
Fourth1971-presentMicroprocessor (VLSI/ULSI)Intel 4004, IBM PC (1981)
Fifthpresent and beyondArtificial intelligenceAI systems, robots

Tip: Books differ slightly on the years. The technology order never changes, so answer by technology.

02

What each technology was

  • Vacuum tube: a sealed glass bulb that controls electric current. ENIAC used about 18,000 tubes. It filled a room and gave off huge heat.
  • Transistor: a tiny solid switch invented in 1947 at Bell Laboratories by Bardeen, Brattain and Shockley. It was smaller, cheaper and more reliable than a tube.
  • Integrated Circuit (IC): many transistors printed together on one silicon chip. Jack Kilby made it in 1958.
  • Microprocessor: the whole CPU on one chip. Intel 4004 (1971) was the first commercial microprocessor.
  • Fifth generation: still growing. Its ideas are artificial intelligence, parallel processing, natural-language input, robotics and quantum research.
03

Features of each generation

GenerationWhat marks it
FirstMagnetic drums. Only machine language (0s and 1s). Programs fed by plugs and switches
SecondMagnetic core memory. Assembly language and first high-level languages (FORTRAN, COBOL)
ThirdKeyboard and monitor. Operating systems appeared. Many users could share one machine
FourthSemiconductor RAM. GUI, personal computers, networks
FifthAI, parallel processing, natural-language and voice input, robotics

Rule: Each generation brought one big software jump. Second got high-level languages. Third got operating systems. Fourth got the GUI.

04

Firsts that exams repeat

Read the exact word in the question. Each word points to a different machine.

Word in the questionMachine
First electronic digital computerABC (Atanasoff-Berry Computer, 1942). It was special-purpose
First general-purpose electronic computerENIAC (1946), by J. P. Eckert and John Mauchly
First stored-program computer (practical)EDSAC (1949, Cambridge)
First commercial computerUNIVAC-I (1951)
First microprocessorIntel 4004 (1971)

ENIAC stands for Electronic Numerical Integrator And Computer. John von Neumann proposed the stored-program design for EDVAC.

Watch: ENIAC came before UNIVAC-I, but ENIAC was never sold. So "first commercial" is UNIVAC-I.

05

Question types you will see

Each type: how to recognise it, the method step by step, and one question to try.

Type 1very common2 practice Q

Generation and core technology

How to spot it:

The question names a technology (vacuum tube, transistor, IC, microprocessor, VLSI) and asks the generation. Or it gives a generation and asks the technology.

Method

  1. Write the ladder: tube, transistor, IC, microprocessor, AI.

  2. Number the rungs 1 to 5.

  3. Match the option to its rung.

  4. Watch the pairs: transistor is 2nd, IC is 3rd.

Why it works:

Each generation is defined by exactly one switching technology.

Try this

Which technology was the basic switching part of third-generation computers?

Show solution

  1. Ladder: tube (1st), transistor (2nd), IC (3rd).

  2. Kilby's ICs put many transistors on one silicon chip.

Answer

Integrated Circuits (ICs)

Type 2common3 practice Q

Famous machine and its generation

How to spot it:

A named machine such as ENIAC, UNIVAC-I, IBM 1401, IBM 360 or Intel 4004 is given. The question asks its generation or role.

Method

  1. Recall the table row that holds the machine.

  2. ENIAC, EDVAC, UNIVAC-I: first generation.

  3. IBM 1401, IBM 7094: second. IBM 360, PDP-8: third.

  4. Match by the technology inside, not by the year.

Why it works:

Every machine belongs to the generation of its switching part.

Try this

The IBM 1401, a business computer of the late 1950s, belongs to which generation?

Show solution

  1. The IBM 1401 is in the second-generation row.

  2. Second generation used transistors.

Answer

Second generation

Type 3very common3 practice Q

'First' in computing history

How to spot it:

Words such as first commercial, first electronic, first microprocessor or first stored-program appear with machine names as options.

Method

  1. Underline the exact adjective in the question.

  2. Electronic digital: ABC. General-purpose electronic: ENIAC.

  3. Stored-program: EDSAC. Commercial: UNIVAC-I. Microprocessor: Intel 4004.

  4. Cross out famous machines that fit a different adjective.

Why it works:

One adjective points to one machine. A different adjective points to another.

Try this

Which machine is regarded as the first commercial computer?

Show solution

  1. The key word is commercial.

  2. UNIVAC-I (1951) was sold to businesses. ENIAC (1946) was not sold.

Answer

UNIVAC-I

Type 4common3 practice Q

Generation features and statements

How to spot it:

A statement question asks about heat, size, machine or assembly language, operating systems, GUI or the fifth generation.

Method

  1. Name the generation the statement talks about.

  2. Read that generation's row in the features table.

  3. Test each option against the row.

  4. Pick the option that matches exactly.

Why it works:

Each generation has a few fixed features, so every statement can be checked.

Try this

Second-generation computers moved away from pure machine language mainly to which languages?

Show solution

  1. Second generation added assembly language.

  2. It also brought early high-level languages FORTRAN and COBOL.

Answer

Assembly language and early high-level languages (FORTRAN, COBOL)

Type 5occasional2 practice Q

Ordering the generations

How to spot it:

Four technologies or four generations must be put in time order. Or the question asks which generation came directly after another.

Method

  1. Write the ladder first.

  2. Give each option a rung number.

  3. Read the option letters in rung order.

Why it works:

The ladder is fixed, so ordering is only a matching job.

Try this

Arrange in time order: A. Integrated Circuit B. Vacuum tube C. Microprocessor D. Transistor

Show solution

  1. Vacuum tube is B (1st).

  2. Transistor is D (2nd), IC is A (3rd), microprocessor is C (4th).

Answer

B, D, A, C

Type 6common

Inventions and their years

How to spot it:

The question asks who or where the transistor, IC or vacuum-tube machines came from, or asks a year (1947, 1958, 1971).

Method

  1. Recall the three anchors: transistor 1947, IC 1958, Intel 4004 1971.

  2. Transistor: Bell Laboratories, Bardeen, Brattain, Shockley.

  3. IC: Jack Kilby.

  4. Match the person or place to the invention.

Why it works:

Three dates and three names cover almost every invention question.

Try this

The transistor was invented in 1947 at which laboratory?

Show solution

  1. Recall the transistor anchor: 1947.

  2. It was made at Bell Laboratories by Bardeen, Brattain and Shockley.

Answer

Bell Laboratories

06

Shortcuts that save time

⚡ Generation ladder mnemonic

Vacuum tube, Transistor, IC, Microprocessor, AI. Read the first letters as "Very Tiny ICs Made AI". Five words match five generations in order.

Example

Which technology marks the third generation?

Show solution

  1. Count along the ladder: tube, transistor, IC.

  2. The third word is IC.

Answer

Integrated Circuits (IC)

⚡ Firsts trio

ENIAC 1946 was built. UNIVAC-I 1951 was sold. Intel 4004 1971 shrank the CPU onto a chip. Remember 1946, 1951, 1971.

Example

Which was the first commercially available computer?

Show solution

  1. The word is commercial, so look for the machine that was sold.

  2. ENIAC was never sold.

Answer

UNIVAC-I (1951)

07

Mistakes to avoid

Where most students lose marks on this subtopic.

Mistake 01

Choosing transistor for the third generation.

Transistors are second generation. ICs are third.

Mistake 02

Calling UNIVAC-I the first computer.

UNIVAC-I was the first commercial computer. ENIAC came earlier.

Mistake 03

Placing the microprocessor in the third generation.

The microprocessor (Intel 4004) opens the fourth generation.

Mistake 04

Learning exact years and forgetting the technology.

Years differ between books. The technology order never changes.

Mistake 05

Treating ABC and ENIAC as the same first.

ABC is the first electronic digital computer. ENIAC is the first general-purpose electronic one.

08

Quick revision

Read this the night before the exam.

  • Ladder: Vacuum tube, Transistor, IC, Microprocessor, AI.

  • First: machine language, huge heat. Second: transistor, core memory, assembly, FORTRAN, COBOL.

  • Third: IC, operating system, keyboard, monitor. Fourth: microprocessor, PC, GUI. Fifth: AI.

  • Transistor 1947 (Bell Labs). IC 1958 (Kilby). Intel 4004 1971.

  • ABC first electronic digital. ENIAC first general-purpose. EDSAC first stored-program. UNIVAC-I first commercial.

  • Answer generation questions by technology, not by exact years.

09

Practice: 18 questions

Sets of 10, mixed across the question types above. Every answer has a step-by-step explanation.

Topic test · 10 questions

Suggested time 4 min · wrong answers go to your mistake notebook automatically.

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