OPERATING SYSTEM NOTES

1st Generation (1940s–mid-1950s) — No Operating System

• Hardware: Vacuum tubes and punch cards

• OS Role: Non-existent

• Programming: Done manually in machine language

• Execution: One job at a time, manually loaded

• Examples: ENIAC, UNIVAC

• Key Characteristics:

  • No batch processing

  • Very limited automation

  • Human operators managed all tasks

2nd Generation (mid-1950s–mid-1960s) — Batch Processing Systems

• Hardware: Transistors, magnetic tapes

• OS Development: Primitive OS started appearing

• Job Handling: Batch systems – jobs grouped and processed sequentially

• Programming: Assembly language, Fortran, COBOL

• Key Features:

  • Job Control Language (JCL)

  • Offline input/output (I/O) handling

  • No interaction with users during job execution

Examples:

• IBM 7094 with IBSYS

• General Motors OS (early batch OS)

3rd Generation (mid-1960s–1970s) — Multiprogramming and Time-Sharing

• Hardware: Integrated Circuits (ICs)

• Major Leap: Multitasking introduced

• OS Evolution:

  • Multiprogramming (multiple jobs in memory)

  • Time-sharing (interactive user sessions)

• Key Features:

  • Virtual memory

  • Spooling (Simultaneous Peripheral Operation On-Line)

  • File systems and command-line interfaces

Examples:

• IBM OS/360

• MULTICS (inspired UNIX)

• CTSS (Compatible Time-Sharing System)

4th Generation (1970s–1990s) — Personal Computers and Networking

• Hardware: Microprocessors (Intel 8080, 80286, etc.)

• OS for PCs: Graphical User Interfaces (GUI) emerge

• Networking: Local Area Networks (LANs)

• Key Developments:

  • OS become user-friendly

  • Rise of commercial OS like MS-DOS, Windows

  • UNIX gains popularity for academic and enterprise use

Examples:

• MS-DOS

• Apple Macintosh System Software

• Windows 1.0 to 95

• UNIX (AT&T, BSD variants)

5th Generation (1990s–present) — Distributed, Mobile, and Cloud OS

• Trends:

  • Mobile computing (smartphones, tablets)

  • Distributed systems and cloud computing

  • Virtualization and containerization (e.g., Docker)

• Key Features:

  • Multicore and parallel processing

  • Real-time and embedded OS

  • Internet-connected devices (IoT)

Examples:

• Windows NT to Windows 11

• Linux (Ubuntu, Red Hat, Android)

• macOS, iOS

• Android OS

• Cloud OS: Google Fuchsia, ChromeOS

6th Generation (Emerging/Future) — AI-Driven and Quantum OS

• Possibilities:

  • AI-integrated OS for context-aware systems

  • OS for quantum computing

  • Edge computing and real-time analytics

• Research Areas:

  • Self-healing systems

  • Predictive performance tuning

  • Autonomic computing