Operating Systems

Operating Systems

1. Managing Resources

   • Peripherals
     • Input and output devices
       • Mouse
       • Keyboard
     • Drivers
       • Software used to map commands to the individual peripherlas
     • The programmer doesn't need to know what specific device is being used
   • Printing
     • Spool
       • It keeps the print job in a queue until the printer is ready
       • The program doesn't need to worry if the printer is busy
   • Backing stores
     • The keep backups of important files
     • The OS makes regular backups in the right format.
   • File compression
     • Storing data in a way that saves space (uses fewer bytes)
     • Compresses data allowing more data to be stored on a device
   • Disk de-fragmentation
     • re-arranging file fragments on a physical disk surface (improves load times)
   • Memory (RAM)
     • RAM is split into 'pages'. Each page is presented to its program as if it is the only memory the system has.
     • Prevents programs from snooping on data from other programs
   • Process (multi-tasking)
     • The processor runs the commands from each task separately
     • Two tasks look like they are acting simultaneously

2. Providing an Interface

   • GUI (Graphical User Interface)
     • GUI is used by most PC and phone operating systems
     • The computer's functions are shown to the user and controlled by input devices
     • It looks like the computer is multi-tasking
     • Easy to learn and there's lots of info shown at once.
     • Uses lots of system resources, complexity can cause error.
   • CLI (Command Line Interface)
     • Text-based interface
     • User types commands
     • All operating systems provides a CLI
     • Hard to use
     • Few system resources required and it's easy to automate
     • It's difficult to learn and it's difficult to compare outputs of different programs
   • File Management
     • Files need to be manipulated
     • Operating systems allow the user to: Copy files, move files, delete files, sort files and search for files
   • System Settings
     • Operating systems allow users to alter the settings
     • The settings include: Enabling or disabling specific hardware, changing the volume, adjusting screen resolution, configuring secondary storage
   • Multitasking
     • multitasking is where multiple processors appear to run simultaneously.
     • CPUs don’t generally support this, so the OS simulates it by alternating which processes get CPU time.
     • A GUI will generally allow different processes to run in separate windows, and be displayed side by side.
   • Error Messages and Support
     • When something goes wrong in a program, the user needs to be informed.
     • The programmer may not know how the program is being used
     • The error is passed to the operating system, which then displays it in the most suitable way.
   • Customisation
     • The ability to customise the interface is a feature of most operating systems.
     • Some allow a completely different desktop environment to be installed.
   • Task Management
     • Some provide the user with the option to quit programs, or kill unresponsive processes.
     • Some also allow the user to prioritise certain processes, allowing certain apps to use the full processor speed.