Nature of Applications

• Systems Software:

  Needed by the system to control hardware and run applications

  • operating system
  • utilities
  • libraries
  • translators
• Utility Programs


  Utility programs optimise the performance of the computer and perform useful background tasks

  • disk defragmenter
  • automatic backup
  • automatic updating
  • virus checker
  • compression software
• Disk Defragmenter


  Large files stored on a magnetic disk may be split up across several physical disk locations. The disk defragmenter reorganises the hard drive so that files are in sequential blocks where possible. The result allows files to be read more quickly.
• The disk defragmenter will try to ensure all parts of file A are contiguous by moving other files as necessary
• Automatic Backup


  Data in permanent storage needs to be regularly backed up. As users may forget it can be automated instead.
• Automatic Updating


  Runs in the background detecting software update releases and automatically installing them. Some updates add new software features others fix security issues which could be exploited by hackers.
• Virus Checker


  Scans permanent storage for viruses by comparing files to known virus definitions. Must be kept up to date on new virus definitions for it to be effective. Antivirus software uses heuristics - it knows what types of behaviour are likely to be used by a malicious program. Heuristics can be used to guess which programs or files may contain a virus, based on their behaviour. Sometimes a virus check may flag a harmless file as a virus.
• Compression Software


  Reduces file size which can help to send large files across the internet.
• Libraries and Translators


  Allow programs to use pre-written routines and to be translated into executable code.
• Applications Software

  Performs a task to benefit the user. Applications can be divided into categories:

  • general purpose
  • special purpose
  • bespoke
• Off the shelf or bespoke


  Ready made software available to anyone to purchase is known as off the shelf software.

  Software that is custom created for a specific user is known as bespoke software.

  Bespoke software is mostly used by businesses rather than individuals.
• Open Source Software

  Allows anyone to access its source code. The software is open source licensed but free to use. Anyone may modify the software and sell it, on the condition that the software produces is also open source. Different from freeware - software that is free for anyone to use but the source code is not available.
• Closed Source (Proprietary)


  Closed source software does not allow access to source code. Users may pay the person or company who owns the copyright license to use the software. There may be restrictions on how the software is used.