Operating Systems

• •The operating system is the most important software on a computer as it enables the hardware to communicate efficiently with the software and provides an interface for users to interact with the computer

  •Operating systems include Microsoft Windows, Android, iOS, Linux

  •When the computer starts up, the operating system is loaded and performs several key functions

  
• •The operating system is responsible for organising keeping track of files stored on a computer's secondary storage. It uses a hierarchical tree structure.

  
• •The top node of the tree is the root directory. Users have to have special administrative privileges to access the root directory.

  A) Root Directory

  
• •Nodes lower down are either directories, sub directories or files. Every file has a unique path so it can be easily located.

  
• •File permissions are used to control who can access a file and what they are allowed to do with it.

  Read: Allows users to view the contents of a file but cannot change the file or delete the original file. (copies don't apply)

  Write: Allows users to view and change the contents of the file.

  Execute: Allows Users to open a file

  Delete: Allows users to delete a file

  
• •Programs are stored on a hard drive or some other form of secondary storage.

  •They are loaded into the computers main memory in order to be executed.

  •A process is a program that is loaded into main memory and is being executed.

  •Some processes are visible to the end user as application software, but others run unnoticed in the background.

  
• •There are usually several processes loaded into a computer's memory at any one time

  •The operating system is responsible for allocating each of the loaded applications a share of the CPU, main memory and peripherals requires

  •This allows several applications to be available at the same time and is known as multitasking.