Operating Systems

Operating Systems

1. Managing Resources

   • Peripherals
     • A peripheral is a device that is attached to the computer, such as a webcam or memory stick
     • For example, it contains the specific machine code needed to print a specific character on that brand of printer.
   • printing
     • spooling
       • The operating system will then spool the print job (it will keep it in a queue until the printer is ready)
       • If my program needs to print a document, I tell the operating system to print it.
   • backing store
     • Backing stores are storage devices used to keep backups of important files
     • Operating systems can often manage this for the user
     • The OS will make regular backups in the right format an appropriate device (Cloud, Tape or Disk)
   • file compression
     • Operating systems can compress data as it’s saved and decompress it as it’s loaded, allowing more data to be stored on a device.
     • File compression is storing data in a way that keeps the same information but uses less disk space.
   • RAM
     • In order to ensure there is enough memory for each program that is running, Ram is split into “pages”
     • This prevents programs from snooping on data from other programs.
   • Disk De-Fragmentation
     • Disk defragmentation involves re-arranging file fragments on a physical disk surface to improve load times
   • Managing processes
     • Modern processors can execute 4 billion instructions every second. This is more than memory and secondary storage can keep up with
     • While a processor waits for other components to catch up, it is not doing anything
   • Multi-tasking
     • In reality the processor runs commands from each task separately, filling in the time when it is waiting for other components.
     • This is a complex task – simply alternating the instructions will result in memory being overwritten

2. Providing an Interface

   • A GUI (Graphical User Interface)
     • Graphical representations of the computer’s functions are shown to the user and controlled by touchscreen or a mouse and keyboard.
     • Programs often run in windows and several can be shown at the same time.
   • A CLI (Command Line Interface)
     • A CLI is a text-based interface.
     • These are harder to use, but are very lightweight and robust – they use few system resources and are very unlikely to crash or break
   • File management
     • Files need to be manipulated.
     • Operating systems provide an interface to the user which allows them to: Copy files, Move files, Delete files, Sort files, Search for files
   • System settings
     • Operating systems enable the user to easily alter system settings
     • Settings include: Enabling or disabling specific hardware, Changing the volume, Adjusting screen resolutionm, Configuring secondary storage
   • Multi-Tasking
     • Multitasking is allowing multiple processes appear to run simultaneously.
     • CPUs don’t generally support this, so the OS simulates it by alternating which processes get CPU time.
   • Error messages and support
     • However, 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.
     • This produces consistent error handling regardless of what application is being used.
   • Customisation options
     • The ability to customise the interface is a feature of most operating systems.
     • Some provide options to change the colour scheme and desktop background Others allow a completely different desktop environment to be installed.
   • Task management
     • The also 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.
     • Operating systems manage processes and allow multitasking.