mark scheme

• what is not a method for transmitting data?

  • serial
  • simplex
  • parallel
  • parity


  parity
• how is data encrypted using symmetric encryption


  • data is encrypted and decrypted using the same key
  • data is encrypted using an algorithm
  • the algorithm generators the key
  • plain text is encrypted into cipher text
• examples of system software


  • operating system
  • utility software
• examples of application software 


  • word processor
  • spreadsheet
  • database
  • web browser
  • social media app
  • image editor
• difference between software and application software


  • system software manages / maintains the hardware / software
  • application software allows the user to perform tasks
• instruction set


  a list of machine codes commands that can be processed by the cpu
• parity check


  an odd or even process can be used
• check sum


  a value is calculated from the data using an algorithm. happens before and after transmission
• echo check


  a copy of the data is sent back to the sender by the receiver
• ARQ


  acknowledgement and timeout are used
• check digit


  a value is appended to data that has been calculated using the data. checked on data entry
• prevention of DDos attack


  proxy server
• why is secondary storage needed


  • to store data/files permanently
  • .. otherwise, data / programs would need to be downloaded every time the computer was used
  • to allow software to be installed on the computer
  • for the creation of virtual memory