Part 1
Introduction
1.1 What is an operating system
1.2 History of operating systems
1.3 Computer hardware review
1.4 The operating system zoo
1.5 Operating system concepts
1.6 System calls
1.7 Operating System Structure
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1.1 What is an operating system

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What is An Operating System
A modern computer consists of:
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One or more processors
Main memory
Disks
Printers
Various input/output devices

Managing all these components requires a layer of software – the operating system
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What is an Operating System

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The Operating System as an Extended Machine
- Hides the messy details which must be performed
- Presents user with a virtual machine, easier to use

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The Operating System as a Resource Manager
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Allow multiple programs to run at the same time
Manage and protect memory, I/O devices, and other resources Includes multiplexing (sharing) resources in two different ways:
• In time
• In space

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1.2 History of Operating Systems

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History of Operating Systems
• First generation 1945 - 1955
– vacuum tubes, plug boards

• Second generation 1955 - 1965
– transistors, batch systems

• Third generation 1965 – 1980
– ICs and multiprogramming

• Fourth generation 1980 – present
– personal computers
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History of Operating Systems
First generation 1945 - 1955
• Computers:ENIAC, UNIVAC…
• Operating System: No OS,
• Machine Language: plugboards
• Single group: designed, built, programmed, operated and maintained each machine

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History of Operating Systems
Second Generation 1955 – 1965 (1)
• Computers: IBM 1401, IBM 7094…
• Operating System : FMS (Fortran Monitor
System), IBSYS for Computer 7094
• Batch Systems
– Function of Early Batch System
– Structure of a typical FMS job
• Separation between designers, builders, programmers, operators and maintenance