Memory

• Computer Memory


  Storage space in the computer, where data is to be processed and instructions required for processing are stored
• Memory


  • Divided into a large number of small parts called cells
  • Each location or cell has a unique address, which varies from zero to memory size minus one
• Types of memory

  • Cache Memory
  • Primary Memory/Main Memory
  • Secondary Memory
• Cache Memory


  • Very high speed semiconductor memory which can speed up the CPU
  • Acts as a buffer between the CPU and the main memory
  • Used to hold those parts of data and program which are most frequently used by the CPU
• Advantages of Cache Memory

  • Faster than main memory
  • Consumes less access time as compared to main memory
  • Stores the program that can be executed within a short period of time
  • Stores data for temporary use
• Disadvantages of Cache Memory

  • Limited capacity
  • Very expensive
• Primary Memory (Main Memory)


  • Holds only those data and instructions on which the computer is currently working
  • Has a limited capacity and data is lost when power is switched off
  • Generally made up of semiconductor device
  • Slower than registers
• Characteristics of Main Memory

  • Semiconductor memories
  • Known as the main memory
  • Usually volatile memory
  • Data is lost in case power is switched off
  • It is the working memory of the computer
  • Faster than secondary memories
  • A computer cannot run without the primary memory
• Secondary Memory

  • Also known as external memory or non-volatile
  • Slower than the main memory
  • Used for storing data/information permanently
  • CPU directly does not access these memories, instead they are accessed via input-output routines
  • Contents of secondary memories are first transferred to the main memory, and then the CPU can access it
• Characteristics of Secondary Memory

  • Magnetic and optical memories
  • Known as the backup memory
  • Non-volatile memory
  • Data is permanently stored even if power is switched off
  • Used for storage of data in a computer
  • Computer may run without the secondary memory
  • Slower than primary memories