Primary Storage (memory)

• Two items stored in the ROM

  1. The BIOS (basic input/output system)
  2. The firmware
• What is primary storage?

  Memory that can be accessed directly by the CPU.
• RAM

  • Volatile- All data is lost when the power is turned off
  • Used for the computer's working memory for instructions, programs and data
  • Can be written to, and read from
• ROM

  • Non-volatile- Data is permanently retained without power
  • Used for the computer's start-up instructions and in embedded systems
  • Read only, so cannot be written to
• RAM is the computer's temporary working memory.
• ROM is stores instructions and data that never need to be changed, such ay the computer's start-up instructions so that it knows what to do when you push the "on" button.
• What does ROM stand for?

  Read Only Memory
• What does RAM stand for?

  Random Access Memory
• Why is virtual memory needed in a system?

  If there are too many applications open at once, or if a particularly memory-intensive application is being used (or both).
• How does virtual memory work?

  Transfers data between RAM and secondary storage when RAM is full
• Using virtual memory can make a computer slow to respond when switching between applications (while data for one application in virtual memory is swapped with the other) or when using a memory-intensive application (due to data constantly moving between virtual memory and RAM just to keep the program running).
• Cache

  Quick access memory inside the CPU
• Virtual memory is used when the computer has no more available random access memory (RAM).
• Using virtual memory makes a computer run slower, as the processor has to wait while data is swapped between hard disk and RAM. As secondary storage devices have slower access times than RAM, the computer's processing performance can be severely impaired. Processing performance can be improved by increasing the size of the RAM, thereby reducing the need for virtual memory.
• Explain why a computer needs both primary and secondary storage.

  Primary

  • To store data / instructions that the processor needs to access.
  • To store the currently running data / instructions

  Secondary

  • To store data / files long-term
  • Store data not current being used