Operating Systems Introduction

Operating Systems Introduction

1. What's an OS

   • Virtualises your computer
     • OS is a program (C/C++)
       • Provides CONSISTENT way of accessing application programs (draw on screen, access hard disk, interact via mouse/keyboard)
       • Resource allocator
         • Manages resources + conflicting requests
       • Control program
         • Controls execution of programs
   • Four components of a computer system
     • Users
       • People, machines, other computers
     • Application Programs
       • Define the ways in which the system resources are used to solve the computing problems of the users (word processors, browsers etc.)
     • Operating system
       • Controls + coordinates use of the hardware among various applications and users
   • Kernel
     • One program constantly running
       • Bootstrap program - First code executed
         • In firmware
         • Loads OS kernel

2. OS Objectives

   • 1. Hide details of hardware by creating abstraction
     • Reasons for abstraction
       • 1. Standardise code with device drives to talk to different peripheral devices
       • 2. OS introduces new functions so programs don't deal with disks
       • 3. OS transforms hardware into multiple virtual computers each for a different program
       • 4. OS can enforce security
   • 2. Allocate resources to processes (manage resources)
   • 3. Provide effective user interface

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