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📘 Operating System – Chapter 1: History of Operating Systems

🧩 Topic: Zeroth Generation – Mechanical Parts

🔹 Zeroth Generation Computers (Before 1940)

  • Also known as the mechanical generation.
  • Time period: 1642 to early 1940s.
  • No operating systems existed; all work was manual.

🛠️ Mechanical Devices Used

These machines were purely mechanical, made using gears, levers, and mechanical parts. No electronics or electricity were involved.

  1. Abacus (circa 2400 BC)

  2. The earliest known computing tool.

  3. Used beads and rods to perform arithmetic calculations.

  4. Not a computer but considered the first step toward automated calculation.

  5. Pascaline (1642) – by Blaise Pascal

  6. A mechanical calculator that could perform addition and subtraction.

  7. Operated using rotating wheels.

  8. Leibniz Calculator (1671) – by Gottfried Wilhelm Leibniz

  9. Improved Pascal’s machine to perform multiplication and division.

  10. Introduced the stepped drum mechanism.

  11. Jacquard Loom (1801) – by Joseph Jacquard

  12. Used punched cards to control weaving patterns in textiles.

  13. Concept of programmable machines introduced here.

  14. Difference Engine (1822) – by Charles Babbage

  15. Designed to compute and tabulate polynomial functions.

  16. Considered the first automatic mechanical computer.

  17. Analytical Engine (1837) – also by Babbage

  18. A general-purpose computing machine.

  19. Had ALU, control flow, and memory – components of modern computers.
  20. Could be programmed using punched cards (idea from Jacquard loom).

⚙️ Key Characteristics of Zeroth Generation Machines

Feature Description
Power Source Manual / Mechanical (No electricity)
Programming Not applicable / Fixed mechanical functions
Speed Very slow
Storage No internal memory
User Interaction Fully manual operation

📌 Summary

  • Zeroth generation computers were purely mechanical.
  • Focused on basic arithmetic operations.
  • No concept of operating systems yet.
  • Foundation laid for programmable computation using punched cards and logic design.

🧩 Topic: First Generation – Vacuum Tubes (1940s–1956)

🔌 Overview

  • Time Period: 1940 to 1956
  • Hardware used: Vacuum Tubes
  • This was the first true electronic computer era.
  • Operating systems: Did not exist yet – all operations were manual.

🔋 What are Vacuum Tubes?

  • Glass tubes used to amplify or switch electronic signals.
  • Used in place of mechanical relays.
  • Large, bulky, generated a lot of heat, and often failed.

🖥️ Key Characteristics of First Generation Computers

Feature Description
Main Component Vacuum Tubes
Size Very large – occupied entire rooms
Speed Thousands of instructions per second
Programming Language Machine language (binary 0s and 1s)
Input/Output Devices Punched cards, paper tape, printers
Memory Magnetic drums or delay lines
Reliability Low – frequent vacuum tube failures
Cost Very expensive to build and operate
Operating System None – programs loaded and executed manually

💻 Important Computers of This Era

  1. ENIAC (1946) – Electronic Numerical Integrator and Computer

  2. First general-purpose fully electronic digital computer.

  3. Built by Mauchly and Eckert.
  4. Used \~18,000 vacuum tubes.

  5. Required manual rewiring to change programs.

  6. EDVAC (1949) – Electronic Discrete Variable Automatic Computer

  7. First computer to use the stored program concept.

  8. Inspired by John von Neumann’s architecture.

  9. UNIVAC I (1951) – Universal Automatic Computer

  10. First commercial computer in the U.S.

  11. Used for business and government applications.

🧠 Limitations

  • No multitasking or resource management.
  • Programs executed sequentially, one at a time.
  • No operating system to automate job scheduling or memory handling.

📌 Summary

  • First generation computers were electronic but primitive.
  • Used vacuum tubes for processing and punched cards for input/output.
  • Programs were written in machine language.
  • No operating systems – everything was manually controlled.
  • Laid the foundation for second-generation computers and OS development.

🧩 Topic: Second Generation – Transistors (1956–1964)

🔌 Overview

  • Time Period: 1956 to 1964
  • Hardware used: Transistors (replaced vacuum tubes)

  • Beginning of simple Operating Systems

  • OS started to appear to manage I/O, scheduling, and job sequencing.

⚙️ What are Transistors?

  • Semiconductor devices used to switch or amplify electronic signals.
  • Invented in 1947 at Bell Labs, widely used in computers by mid-1950s.
  • Much smaller, faster, reliable, and more energy-efficient than vacuum tubes.

🖥️ Key Characteristics of Second Generation Computers

Feature Description
Main Component Transistors
Size Smaller and more compact than first generation
Speed Hundreds of thousands of instructions per second
Programming Language Assembly language (low-level, symbolic)
Input/Output Devices Punched cards, printers, magnetic tape
Memory Magnetic core memory
Cost Cheaper and more reliable than vacuum tubes
Operating System First OS developed for basic job processing

🧠 Operating System Features Introduced

  • Batch processing:

  • Jobs grouped and run in batches without manual intervention.

  • Job Control Language (JCL):

  • Used to control the execution of batch jobs.

  • Basic I/O management:

  • OS could handle simple input/output device communication.

  • Automatic job sequencing:

  • Reduced human operator effort to run each program manually.

💻 Examples of Second Generation Computers

  1. IBM 1401 (1959)

  2. Most widely used business computer of the time.

  3. Used magnetic tape for storage.

  4. IBM 7090

  5. Used in scientific and technical fields.

  6. High-speed transistorized computer.

🧩 Limitations

  • No interactive user interface.
  • No multitasking – jobs ran one after another.
  • OS was still primitive – just job automation and I/O handling.

📌 Summary

  • Second generation introduced transistors and basic operating systems.
  • Programming moved from machine to assembly language.
  • First use of batch processing and job control.
  • Marked the beginning of OS as a system software component.

🧩 Topic: Third Generation – Integrated Circuits (1964–1971)

🔍 Overview

  • Time Period: 1964 to 1971
  • Hardware used: Integrated Circuits (ICs)
  • Major shift toward multiprogramming and time-sharing.
  • Operating Systems became more advanced and general-purpose.

🔌 What are Integrated Circuits (ICs)?

  • An IC combines multiple transistors, resistors, and capacitors into a single chip.
  • Greatly reduced size, cost, and power consumption.
  • Increased speed, reliability, and processing power.

🖥️ Key Characteristics of Third Generation Computers

Feature Description
Main Component Integrated Circuits (SSI & MSI)
Size Much smaller than second generation
Speed Millions of instructions per second
Programming Languages High-level languages like FORTRAN, COBOL
Memory Magnetic core memory (more refined)
Input/Output Keyboard, monitor, magnetic disks
Operating System Multi-user, multiprogramming, time-sharing
Cost Further reduced, more accessible

🧠 Operating System Advances

  1. Multiprogramming OS

  2. Multiple programs loaded into memory at once.

  3. CPU switches between jobs to maximize utilization.

  4. Time-sharing OS

  5. Multiple users can interact with the system simultaneously.

  6. Each user gets a small slice of CPU time → illusion of parallel use.

  7. Spooling

  8. Simultaneous Peripheral Operation On-Line.

  9. Input/output operations performed concurrently with processing.

  10. Job Scheduling

  11. OS decides which job to run next using scheduling algorithms.

  12. Memory Management

  13. Efficient allocation and protection of memory for multiple users/programs.

💻 Examples of Third Generation Computers

  1. IBM System/360 (1964)

  2. First family of computers with compatible software/hardware.

  3. Used across business, government, and science.

  4. PDP-11 (1970) – by Digital Equipment Corporation (DEC)

  5. Popular minicomputer supporting time-sharing.

🚀 Impact on Operating Systems

  • OS became a full-fledged system software component.
  • Introduced support for multi-user, multitasking, and device independence.
  • Basis for modern OS concepts like context switching and resource allocation.

📌 Summary

  • Third generation introduced ICs, enabling smaller, faster, cheaper computers.
  • Multiprogramming and time-sharing emerged.
  • Operating systems became interactive and user-friendly.
  • Marked the shift from batch processing to interactive computing.

Here’s your exam-ready note for:

🧩 Topic: Fourth Generation – Large Scale Integration (1971–Present)

🧠 Overview

  • Time Period: 1971 to Present
  • Hardware used: Large Scale Integration (LSI), Very Large Scale Integration (VLSI)
  • Led to the development of microprocessors, personal computers (PCs).
  • Modern Operating Systems began to emerge.

💡 What is Large Scale Integration (LSI)?

  • LSI technology allows thousands of transistors to be integrated onto a single silicon chip.
  • VLSI followed, allowing millions of components on a chip.
  • Enabled the creation of microprocessors, making computers small, affordable, and powerful.

🖥️ Key Characteristics of Fourth Generation Computers

Feature Description
Main Component LSI/VLSI Chips, Microprocessors
Size Small (Desktop & Laptop PCs)
Speed Millions to billions of instructions per second
Programming Languages High-level (C, C++, Java, Python, etc.)
Input/Output GUI, mouse, touchscreens, SSDs, USB devices
Cost Affordable for individuals and businesses
Networking Internet, LAN/WAN support
Operating System Graphical, multiuser, multitasking, networked

🧠 Operating System Developments

  1. Graphical User Interfaces (GUI)

  2. OS with visual interface (Windows, macOS, GNOME)

  3. Easy interaction using mouse, icons, and windows.

  4. Multitasking & Multiuser OS

  5. Handle multiple applications and multiple users efficiently.

  6. Real-time OS

  7. Used in embedded systems, IoT devices, robotics.

  8. Distributed OS

  9. Manages resources across multiple networked computers.

  10. Mobile & Embedded OS

  11. Android, iOS, Embedded Linux power smartphones, smart devices.

  12. Security & Virtualization

  13. Built-in firewalls, authentication, and virtual machines (VMware, KVM).

💻 Examples of Fourth Generation Computers & OS

System Description
Intel 4004 (1971) First commercial microprocessor
IBM PC (1981) Revolutionized personal computing
Microsoft Windows GUI-based OS used globally
Linux (1991) Open-source, powerful OS for servers & desktops
Android, iOS Mobile operating systems

📌 Summary

  • Fourth generation began with microprocessors and LSI chips.
  • Birth of personal computing and user-friendly OS.
  • OS now supports networking, security, multitasking, and GUIs.
  • Foundation for modern cloud, AI, mobile, and IoT platforms.