Unit 1.3: Generations of Computers | IT 231

Learning Objectives

By the end of this chapter, you will be able to:

• Describe the five generations of computers and their defining technologies.
• Explain the evolution from vacuum tubes to modern microprocessors.
• Identify key developments and limitations of each generation.
• Understand current and emerging computing technologies.

Overview of Computer Generations

The evolution of computers is typically divided into five generations, each defined by a major technological advancement. With each generation, computers became smaller, faster, more powerful, more energy-efficient, and more affordable.

First Generation (1940-1956): Vacuum Tubes

The first generation of computers used vacuum tubes as their primary electronic component for circuitry and magnetic drums for memory.

Characteristics

• Technology: Vacuum tubes (thermionic valves)
• Size: Room-sized machines weighing tons
• Speed: Measured in milliseconds
• Memory: Magnetic drums, typically 2KB
• Input/Output: Punched cards and paper tape
• Programming: Machine language (binary code)
• Power: Consumed enormous amounts of electricity
• Heat: Generated tremendous heat, requiring air conditioning

Key Examples

• ENIAC (1946): Electronic Numerical Integrator and Computer—the first general-purpose electronic computer
• UNIVAC I (1951): First commercially successful computer
• EDVAC: Introduced the stored-program concept

Limitations

• Extremely large and expensive
• Generated excessive heat
• Frequent hardware failures
• Required specialized facilities
• Programming was tedious and time-consuming

Second Generation (1956-1963): Transistors

The second generation replaced vacuum tubes with transistors, invented at Bell Labs in 1947 but widely adopted in computers by the late 1950s.

Characteristics

• Technology: Transistors (semiconductor devices)
• Size: Smaller than first generation but still room-sized
• Speed: Measured in microseconds
• Memory: Magnetic core memory
• Input/Output: Punched cards, magnetic tape
• Programming: Assembly language and early high-level languages (FORTRAN, COBOL)
• Power: Much lower power consumption
• Reliability: More reliable than vacuum tubes

Key Examples

• IBM 7090: Widely used for scientific applications
• IBM 1401: Popular for business applications
• CDC 1604: Designed by Seymour Cray

Advantages Over First Generation

• 10x smaller than vacuum tube computers
• Generated less heat
• Faster processing speeds
• More reliable and energy-efficient
• Easier to program with assembly language

Third Generation (1964-1971): Integrated Circuits

The third generation introduced integrated circuits (ICs), which combined multiple transistors onto a single silicon chip.

Characteristics

• Technology: Integrated circuits (ICs) or chips
• Size: Significantly smaller, desk-sized computers emerged
• Speed: Measured in nanoseconds
• Memory: Semiconductor memory began replacing magnetic core
• Input/Output: Keyboards and monitors introduced
• Programming: High-level languages (BASIC, Pascal), operating systems
• Features: Time-sharing, multiprogramming

Key Examples

• IBM System/360 (1964): Revolutionary family of compatible computers
• PDP-8: First successful minicomputer
• CDC 6600: First supercomputer

Major Advances

• Introduction of operating systems
• Time-sharing allowed multiple users
• Software industry began to emerge
• Computers became accessible to more organizations

Fourth Generation (1971-Present): Microprocessors

The fourth generation began with the development of the microprocessor—an entire CPU on a single chip.

Characteristics

• Technology: Microprocessors (VLSI - Very Large Scale Integration)
• Size: Desktop and portable computers
• Speed: Measured in picoseconds to nanoseconds
• Memory: Semiconductor RAM/ROM, hard drives, SSDs
• Input/Output: GUIs, mice, touchscreens, voice input
• Programming: Object-oriented languages, 4GLs, visual programming
• Features: Personal computers, networking, internet

Key Milestones

• Intel 4004 (1971): First commercial microprocessor
• Apple II (1977): Early successful personal computer
• IBM PC (1981): Set the standard for personal computing
• World Wide Web (1991): Transformed computing and communication

Defining Characteristics

• Graphical User Interfaces (GUIs)
• Personal computers in homes and offices
• Networking and the Internet
• Mobile computing (laptops, smartphones, tablets)
• Cloud computing

Fifth Generation (Present and Beyond): AI and Beyond

The fifth generation focuses on artificial intelligence, parallel processing, and emerging technologies like quantum computing.

Characteristics

• Technology: AI, machine learning, neural networks, quantum computing
• Focus: Natural language processing, voice recognition, intelligent systems
• Goal: Computers that can think, learn, and reason
• Features: Speech recognition, expert systems, robotics

Current Technologies

• Artificial Intelligence (AI): Systems that can learn and make decisions
• Machine Learning: Algorithms that improve through experience
• Natural Language Processing: Understanding human speech and text
• Quantum Computing: Using quantum mechanics for computation
• Internet of Things (IoT): Connected smart devices

Examples

• Virtual assistants (Siri, Alexa, Google Assistant)
• Self-driving vehicles
• AI-powered recommendations
• Facial recognition systems
• IBM Watson, Google DeepMind

Summary Comparison

Generation	Technology	Speed	Language	Key Feature
First (1940-56)	Vacuum Tubes	ms	Machine	Room-sized
Second (1956-63)	Transistors	μs	Assembly	Smaller, reliable
Third (1964-71)	ICs	ns	High-level	Operating systems
Fourth (1971-now)	Microprocessors	ps-ns	OOP, 4GL	Personal computers
Fifth (now+)	AI/Quantum	Beyond ns	Natural	Intelligent systems

Key Takeaways

• Each generation brought dramatic improvements in size, speed, and capability
• The trend continues toward smaller, faster, more intelligent systems
• Modern computing builds upon all previous generations
• The future points toward AI, quantum computing, and ubiquitous connectivity