1. Primary Memory

• • processed data, instructions and all resulting data are stored in the primary memory

  • directly connected to the processor and feeds the processor with the required data by the fetch, decode, executed cycle data and instructions (Machine Instruction Cycle).

  • also referred to as Immediate Access Store.

     A. RAM and Cache Memory

• • • Memory that stores data and instructions temporarily. Instructions and data may be altered at any time.

    • Two types of RAM

      • • static RAM - a memory that holds data for as long as there is power supply to the memory circuits.

        • dynamic RAM - data stored in a dynamic RAM gradually leaks away and needs to be refreshed periodically

     B. ROM (Read Only Memory)

• • • a non-volatile memory which is slower than RAM. 

    • it is used to hold critical instructions which used to start up a system (computer or PC). 

    • a common use of ROM is to hold the Basic Input Output System (BIOS) which makes it possible for  a computer to  boot and sometimes hold the entire Operating System

4. Secondary Storage

• • also called auxiliary storage or backing store 

  • a storage hardware that provides data integrity, low cost, mass storage and permanent storage

  • Types of secondary storage device access

    • • Direct access - 

      • Sequential access - sequential access memory is a class of data storage devices that reads stored data in a sequence (usually in the form of magnetic or optical storage.