Operating System

Operating System

1. Functions

   • Resource Management
     • Acts as resource manager and extended machine. From resource manager point of view efficient use of resources is allowed and from extended machine point of view, computer acts as many virtual computers
   • To hide details of hardware
     • Using abstraction, it is done. i) Device drivers perform I/O operations. ii) Because of abstraction, programs do not have to deal with disks. iii) Computer acts as many virtual machines. iv) Security is enforced using abstraction.
   • Effective user interface
     • Provides an effective user interface. Interface includes command interpreter, file system and online help.

2. Evolution of OS

   • Early Systems
     • Bare h/w
     • No OS
     • First application
       • Artillery table generation
     • Experimental computers
     • One person at a time
     • Same code repeated
     • Debugging
       • Fixing both s/w and h/w
       • Object code rewriting
       • Changing actual computer
     • Research paid by American and British armies
     • Idea to write better drivers
   • Simple Batch Systems
     • PPU was used to read data
     • Punched cards
     • Loading of cards into card reader
     • Similar jobs batched together
     • Implemented by batch monitor
     • Wastage of CPU time
     • Slow reading and printing
     • Considerable delay b/w job submission and completion
     • SPOOL was used to deal with the delay
     • Processor reads and prints the data