1.5.1

• The operating system is software that manages the computer's hardware and provides a user interface
• Functions of the OS:

  • Provides a user interface
  • Memory management and multitasking
  • Peripheral management and drivers
  • User management
  • File management
• User interface:

  • Allows the user to interact with a computer system
• User interface- Graphical User Interface (GUI)

  • User interacts through WIMP (Windows, Icons, Menus and Pointers)
  • Intuitive, reduces the need to learn complex commands.
  • Uses more RAM, processing power and storage space
• User interface- Command line interface:

  • Commands are typed as text
  • No graphics
  • Quicker, more flexible, efficient and powerful for expert users
  • Less resource-heavy - less space on disk and in RAM
  • Not suitable for everyday users
• User interface- Menu driven:

  • e.g. iPod- buttons for up, down, left, right and ok
• User interface- Natural language:

  • Voice activated
  • Becoming increasingly common- e.g. Alexa, Siri
• Memory management:

  • Manages available memory- moves programs and data in and out of memory when needed
• Memory management:

  • Data used by a program is copied from secondary storage to main memory (RAM)
  • The OS keeps a record of where each program and its data are located- it must not overwrite existing programs
  • A memory manager allocates certain applications certain memory addresses to make sure their processes are placed in different locations
  • The OS keeps track of available RAM. When RAM is full the OS allocates secondary storage for virtual memory
• Memory management- multitasking:

  • A computer that can switch rapidly between tasks is a multitasking computer
  • A multitasking OS shares CPU time so efficiently it appears to be processing several programs at the same time
• Peripheral management:

  • Peripherals are any computer hardware components that are not a part of the CPU
  • e.g. input, output and storage devices
• Peripheral management- Drivers:

  • Small programs that act as an interface/translator between the peripheral device and the applications or operating systems that use it
  • Many drivers are built into the OS
• Peripheral management- Buffering:

  • Used to compensate for the differing speeds that data is received and the rate in which the device functions
  • e.g. a computer can send data thousands of times faster than a printer can print it
  • A data buffer is an area of memory (RAM) in either the computer or the peripheral device
• User management:

  • Single user- allow one user to user a computer at once
  • Multi user- allow several users to use the computer at the same time, e.g. ATMs
• User management:

  • The OS allocates accounts, organises user logins and passwords- may include password protection on individual files, controls access rights
  • Access rights- is a computer is used by more than one person, each user should only be able to see their own files. Users and system administrators have different levels of access rights
• User management:

  • Operating systems may have anti-theft measures to prevent other users from accessing locked devices or accounts to steal information.
  • User accounts may be password, or pin protected etc.
• File management:

  • File extensions, e.g. .jpg, .mp3) help the OS determine file types and which application to use when opening files
• File management:

  • The OS is responsible for the organisation of data into a useable hierarchal structure. It also deals with the naming, saving, movement, editing and deletion of data
  • The OS manages the hard disk. It splits the physical disk into storage sectors, decides which sectors to write data to, and keeps track of free space on the disk.
  • Keeps track of where files are so they can be retrieved
  • Makes sure no file overwrites another file