Operating Systems

Operating Systems

1. Features of an Operating System

   • Multitasking
     • Running multiple programs at once by giving each a small time slice of processor time.
     • Allows more than one program to be held in the memory at a time, and data shared between them such as copy and paste.
     • Also enables you to listen to music on your pc at the same time as word processing.
   • Memory Management
     • When programs are loaded the operating system decides where they are held in memory.
     • Over time the memory becomes fragmented as programs are loaded and closed because they use different amounts of memory.
     • The operating system must keep track of different program fragments.
     • When the memory is full the operating systems use virtual memory
   • Device Drivers
     • These translate operating system instructions into commands that the hardware will understand.
     • Each peripheral needs a device driver.
     • Many are already built into the operating systems.
   • User Mangement
     • Provides for different users to log into a computer.
     • The operating system will retain individual settings for each user, such as icons, desktop backgrounds, etc.
     • Each user may have different access rights to files and programs.
     • A client server network may impose a fixed or roaming profile for a user, and manage login requests to the network.
   • File Mangement
     • Data is stored in files.
     • An extension to the filename tells the operating system which application to load the file into.
     • Over time the hard disks becomes fragmented.
     • The operating system may present a logical structure of files into folders, and allow the user to rename, delete, copy and move files.

2. User Interfaces

   • Graphical (GUI)
     • Windows, icon, menus and pointers(WIMP)
     • Visual
     • Interactive
     • Intuitive optimised for mouse and touch gesture input
   • Menu Driven
     • Successive menus presented to the user
     • Single option at each stage
     • Often buttons on a keypad
   • Command Line
     • Text based
     • Less resource heavy compared to GUI
     • More commands than a GUI
     • Efficient
     • For advanced users
     • Useful for automating processes with scripts
   • Natural Language
     • Responds to questions in spoken language
     • Not always reliable
     • E.g. Siri or Alexa