backing storage

  • Main storage is located inside the computer system. it can either be RAM or ROM.
  • Backing storage is outside the main processor, e.g Hard Drives, CD/DVD drives, USB flash memory (pen drives)


  • Rom is used to store a small part of the operating system called the bootstrap loader.
  • Data is stored permanently in ROM
  • Data is not lost when power goes off
  • Data in ROM cannot be changed


  • The term RAM is synonymous with main memory, the memory available to programmes
  • A processor can write to and read from RAM at high speed
  • Data held in RAM can be changed
  • All data in RAM is lost when the power is switched off