Computer Systems

Computer Hardware Lesson III

Lesson Objectives By the end of this lesson you should be able to: State and explain various special purpose memories Define software classify software into various categories  

Special Purpose Memories

There are three types of special-purpose memories:

  1. Buffers
  2. Registers
  3. Cache Memory


These are memories found within input and output devices. They hold data awaiting processing or data that has been processed to free the CPU.


Registers are special-purpose memories located inside the CPU.

Examples of registers

  • The accumulator that holds the result of the last processing step of the ALU
  • The Address register that holds the next piece of data waiting to be processed
  • The instruction register temporarily holds an instruction just before it is interpreted into a form that the CPU  can process.
  • Storage register that temporarily holds a piece of data that is on its way to and from the CPU and the main memory

Computer Software

Computer software refers to a set of instructions that guides the computer on how to perform specific tasks.

Software Classification According to Purpose

  • System software
  • Application Software

System Software

This software is designed to manage system resources and avail them to the user.

System software includes:

  • operating system
  • firmware
  • utility software
  • network software

An operating system is system software that manages the computer hardware and provides a platform for the installation of application software

Firmware refers to the tangible electronic component of a computer with embedded  software for example BIOS in ROM

Utility software is a system software meant to maintain, optimize, and configure a computer.

Networking software is meant to facilitate communication  between two or more computers on a network e.g Network Operating System

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