Software

• System Software


  Software that manages the computer's internal functions
• Functions of system software


  • Storage management
  • Processing time allocation
  • Memory allocation
• Storage management


  Manages the storage of data and files on external devices
• Processing time allocation


  Allocates processing time between programs using time slicing
• Memory allocation


  Organises the use of main memory between programs
• Real-time processing


  Data is processed immediately after it is input, and the output generated influences the next input
• Real-time processing examples


  • Airline booking system
  • Online stock control system
  • Air traffic control
• Batch processing


  Collecting groups of similar data over a period of time and then inputting the data at an agreed time, without user involvement
• Batch processing is suitable when data does not need to be processed immediately, and is usually done when the processor is not busy
• Master file


  Stores information which does not change in the short term, such as customer number and name
• Transaction file


  Stores current data, such as meter readings, and contains the key field of the master file to allow the files to be merged and linked
• The transaction file must be sorted according to the master file
• Multi-user system


  Many users work on different computers but share the same processor of a more powerful computer, with the operating system switching at high speed between the computers to give each one a small amount of processor time (time-slicing)
• Utility software functions


  • Disk defragmentation
  • Backing up and restoring data
  • Task scheduling
• Disk defragmentation


  Rearranges data on the disc so that files are stored in blocks that are all together, and all the free blocks are together in the same part of the disc
• Advantages of disk defragmentation


  • Speeds up access to files
  • Provides more storage space
  • Files are more organised
  • Computer runs quicker
• Task scheduling


  Divides the processor time amongst a number of tasks, so that in a multi-user system each user appears to have interrupted access to the powerful computer, and on a single computer with its own processor, several programs appear to be running at the same time
• Backup and restoring data


  A backup is a copy of the original data or file in case it gets damaged or lost, stored off-site in a secure location, that can be used to restore the original data to its previous state
• Virus


  A program that can attach itself to a file and then spread to other files, and can intentionally damage the computer system, prevent it from booting up or slow down the performance of a computer
• Anti-virus software


  Scans files stored on a computer and data entering a computer system, and compares these to a known database of viruses, to detect and prevent the spread of viruses
• What are examples of Real-Time Processing

  Airline booking system , online stock system and air traffic control system