Overview of Computer Systems

It is an electronic device which accepts data(raw facts) as input, process the data (arithmetically & logical operation) in accordance with a per-defined program and then transfers the processed data to an output device.
the basic unit of a computer are
  • input unit
  • output unit
  • storage unit
  • processing unit

The Input unit 
 It accepts data and instructions from the user into the computer systems.  It accepts commands fro running or aborting a program from the user.
The Storage unit 
 it retains a copy of the information and data to be  processed 
The Processing unit 
 it converts data(a raw fact) in to information
The Output unit 
 It transmits intermediate and final results to the user from the computer system

  • Speed – their high  speed enables the computer to process and manipulate data faster. 
  • Accuracy   GIGO – Garbage in Garbage Out 
  • Consistency – given the same data and instructions it will produce same results every time that particular process is repeated. (GIGO)
  • Ability - to store large volumes o data. Data is stored on various media that run on devices connected to a computer such as discs 

Computers are classified by:-
  1. Type of data they manipulate e.g. digital and Analogue computers and hybrid computers.
  2. The purpose for which they are designed e.g. General & Special purpose.
  3. on the basis of price , size and other capabilities
 (a)Type of Dara the manipulate
  •   Analogue Computers They perform arithmetic operations and logical comprises by measuring changes in physical magnitude.    Example of an analogue device is speedometer.  
  • Digital computers They are the most commonly used type of computers.  The arithmetic operations and logic comparisons are basic on binary digits zero and ones (0&1). 
  •  The hybrid computers  They are designed by interconnecting digits and analogue directly into worked processor using a suitable interface circuitry.  e.g. in a hospital ICU  devices
(b) The purpose for which they are designed

  •   Special Purpose Computers They are digital computers designed to carry out a special processing task in one or more applications e.g. a savor in a network.
  •     General Purpose Computers They are designed to be used in a variety of application environment as required.  

(c) on the basis of price , size and other capabilities
a) Main frame computers They are the most expensive of all computers.  They are big n size and offer maximum computing power.   They handle all kinds of problems both scientific and commercial.  They have large online secondary storage capabilities and can support a number and variety of peripheral devices.
b) Mini computers They are medium sized; smaller than main frame but bigger than micro computers.  They support average internal and backing storage devices, support several users at a time  They are cheaper than the main frame, are used in medium scale business 
c) The Micro computers They are the most common form of computers in offices today as desktop, personal and stand alone systems.  They are the smallest of the three computer classes. Compared to the others, their internal memory is smaller have united backing storage media and are cheaper.

  1. Operates as a high speed ie. Faster processing.
  2. Results are accurate.
  3. Works continuously without getting tired/.
  4. They work on voluminous data.
  5. They can work on any problem provided relevant instructions are given.
  6. Operates in risky environment which are risky to human life.
  7. Its flexible i.e. can adapt to any work load without any strain.
  8. stores a large volume of data depending on the memory
  9. Helps produce paperwork significantly i.e office automation.
  10. Reduce the number of personnel needed to carry out various organizations activities hence a cost saving.
  11. Reduce requirements of office space which is otherwise required.