Operating System

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  • Systems Software
    • OS
      • Device Drivers
        • Allows operating systems to communicate with hardware
        • Essentially acts as a translator between hardware and software
      • User Interface
        • Allows the user to interact with a computer system
        • Graphical User Interface are the most popular as they are visual and interactive
      • Multitasking
        • The OS helps the CPU carry out multitasking by efficiently managing memory and CPU processing time
          • When an application is opened, the OS moves the neccesary parts to memory, followed by required additional parts.
            • To run multiple applications, the OS makes sure the applications don't interfere. It does this by using a memory manager to allocate memory addresses.
              • Only one application can be processed at any time so the OS divides CPU time into the most efficient order
                • When required, the OS moves data to and from virtual memory
      • File and Disk Management
        • File Management is the organisation of data into a usable hierarchical structure
        • The hard disk is also managed, it splits the physical disk into storage sectors, decides which sector to write data and keeps track of free space
          • Ideally the data for a single file would be placed in adjacent sectors, but this isn't always possible
      • User Accounts
        • Single-User: Only allow one user on at once, most common type of OS even if there are multiple accounts
        • Multi-User: Allow several people on at once. Mostly used by mainframes such as ATMs
        • Responsible for user account control - allow different users to gain access to their own information but not to other user's information stored on the same system
        • Often has some form of anti-theft measures - such as passwords or pins. Some systems have fingerprint or retina scanners
    • Utility Software
      • Disk Defragmentation
        • As files are moved, deleted, or change size lots of small gaps appear which new files fill in. Over time, the hard drive becomes more fragmented which slows the performance down.
          • Defragmentation software reorganises data to put fragmented files together. It also moves files to collect all of the free space.
          • Fregmented files does not affect SSDs as they have no moving parts.
      • Backup Utilities
        • Backup utilities allow for scheduling of regular backups, creating rescue disks and options for full or incremental backups
        • Full backups are when a copy of every file is taken, this uses a lot of storage space but is faster to restore from
          • Incremental backups are when only the files created or edited since the last backup are copied. This saves time and space but will take longer to restore.
      • Compression Software
        • Reduces the size of files. Used frequently on the internet as .zip and .rar files. Need to be extracted before the can be used
      • Encryption Software
        • Scrambles data to stop third-parties from viewing it. Can be decryption using a special 'key'




quite a session

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