Types and components of Computer Systems

—  Candidates should be able to

·         define hardware, giving examples

·         define software, giving examples

·         describe the difference between hardware and software

·         identify the main components of a general-purpose computer: central processing unit, main/internal memory (including ROM and RAM), input devices, output devices and secondary/backing storage

·         identify operating systems, including those which contain a graphical user interface, a command line Interface

·         identify different types of computer including Personal Computer or desktop, mainframe, laptop, palmtop and Personal Digital Assistant

·         describe recent developments in ICT

What is Computer?

A computer is an electronic device that receives input, stores it for a period of time, operating it according to a set of instructions (Known as a PROGRAM) and gives the user with an output.

Computer is an electronic device which converts data into information.

Types of Computers

Computers come in all sorts of shapes and sizes.  Based on Capacity, speed and reliability computers can be divided into the following categories of computers:

—  Palmtop

—  Laptop

—  Personal/Desktop

—  Mainframe, and

—  Super Computer

Computer System

A computer system is the combination of hardware and software. A typical computer system has memory and set of states that define the relationship between the system's inputs and outputs.

—  FEATURES OF COMPUTER

—  Speed

—  Accuracy

—  Storage

—  Versatility

—  Automation

—  Diligence

—  LIMITATIONS OF A COMPUTER

Computer is as intelligent as is the program that runs it. Without a program computer is useless.

Computer cannot detect wrong feeding of data.

Computer Components

The Computer System has two main components which when both combined makes a computer system. These are

—  Hardware

—  Software

Hardware

Hardware means the physical structure of a computer, i.e., the parts that can be touched by us. All the components attached to the computer like Keyboard, Mouse, Monitor, Printers are hardware.

Software

Hardware is just a box with electronic parts in it. It cannot do any work by itself. It needs certain programs to do some work. Software is a general term used to describe a collection of computer programs, procedures and documentation that perform some tasks on a computer system. Software includes websites, programs, video games etc.    

The Difference Between Hardware and Software

—  Computer hardware is the physical components that make up the computer system. Hardware is useless without software to run on it.

—  Software is instructions that tell computer hardware what to do. Software is useless unless there is hardware to run it on.

—  For a computer system to be useful it has to consist of both hardware and software.

Hardware Components

                We can categorize hardware components in three broad categories:

·         Input Devices

·         CPU, the Central Processing Unit, and

·         Output Devices

·         [Backing] Storage Devices or Secondary Memory

—  Input Devices

Input devices are used to put data and instructions into a computer. Most common input devices are keyboard and mouse.

—  Central Processing Unit

CPU stands for Central Processing Unit. It is a small chip inside the computer. It does all decisions, calculations. It also controls other parts of a computer. CPU consists of several section:

      1. Control Unit (CU)
      2. Arithmetic and Logic Unit (ALU)
      3. Main Memory

1. Control Unit - Control Unit controls operations of other parts of CPU as well as all parts of computer by sending a control signal, e.g.

—  control sequence of instruction to be executed

—  control flow of data among all parts of computer

—  interpret instructions

—  regulate timing of procressor

—  send control single to and recieve control single from peripheral devices

2. Arithmetic and Logic Unit- Arithmetic and Logic Unit consist of a complicated set of logic circuit and accumulator. It is mainly responsible for

—  Calculation

—  Logical comparison and decision

3. Main Memory - The main memory holds the program instructions and data. It contains two types of memory chip, called ROM and RAM.

           Random Access Memory (RAM) is the part of the computer that temporarily stores the instructions that the computer is running, and the data it is processing. RAM is a volatile storage device.  When a computer is in use, its RAM will contain…

·         The operating system software

·         The application software currently being used

·         Any data that is being processed

           Read-Only Memory (ROM) is used in most computers to hold a small, special piece of software: the 'boot up' program. This software runs when the computer is switched on or 'boots up'. The software checks the computer’s hardware and then loads the operating system. ROM is non-volatile storage.

—  Output Devices

Output devices are used to get the result of the processing done by the computer. Most common output devices include monitor and printer.

—  Storage Devices

Secondary or backing storage is used to store programs and data when they are not being used i.e. used to store permanently. Secondary storage is non-volatile, so data that is stored on these devices remains there safely.

A hard drive, a CD-ROM, a floppy disc and a USB memory stick are all examples of secondary storage devices.

—  Peripheral Devices

Peripheral devices are not part of the central core of the computer. The general name for extra/additional devices is ‘peripheral devices’. They are usually categorized into input devices, output devices and storage devices.

CD-ROM drive, Mouse, Printer, Speaker, Scanner, Zip drive are some examples of peripheral devices.

—  Types of Software

—  Application Software

—  System Software

—  Utility Software

System Software -    A system software package is a collection of programs designed to operate, control, and extend processing capabilities of computers.

Operating System is one of the system software.

Application Software- An application software is a set of programs that allow computer to perform a specific data-processing job for the user.

Special Purpose Software

General Purpose Software

Utility Software -   Utility software is special purpose software that improves the operations of system software by providing additional and specialized functionality to it. It helps to keep your system in shape by eliminating/correcting error.

—  Operating Systems

An Operating System is the most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers.

Operating systems provide a software platform on top of which other programs, called application programs, can run. The application programs must be written to run on top of a particular operating system. Your choice of operating system, therefore, determines to a great extent the applications you can run.

In any computer, the operating system:

—  controls the backing store and peripherals such as scanners and printers

—  deals with the transfer of programs in and out of memory

—  organizes the use of memory between programs

—  organizes processing time between programs and users

—  maintains security and access rights of users

—  deals with errors and user instructions

—  allows the user to save files to a backing store

—  User Interfaces

A user interface is the method by which the user and the computer exchange information and instructions. There are two main types:

        1. Command Line or Character User Interface (CUI)
        2. Graphical User Interface (GUI)

Command-line interfaces- A command-line interface allows the user to interact with the computer by typing in commands-set of instruction. The computer displays a prompt, the user keys in the command and presses enter or return. An example of a common command driven interface is MS-DOS.

                Features of a command-line interface

—  Commands must be typed correctly and in the right order or the command will not work.

—  Experienced users who know the commands can work very quickly without having to find their way around menus.

—  An inexperienced user can sometimes find a command driven program difficult to use because of the number of commands that have to be learnt.

Graphical user interfaces- Graphical user interface is sometimes shortened to GUI. The user chooses an option usually by pointing a mouse at an icon representing that option.

Features of GUIs include:

—  They are much easier to use for beginners.

—  They enable you to easily exchange information between software using cut and paste or 'drag and drop'.

—  They use a lot of memory and processing power.

When discussing user interfaces, it is important to note that Windows XP, Windows Vista, Apple OSX and Ubuntu all have graphical user interfaces.

           Windows XP: an operating system by Microsoft

           Windows Vista: an operating system by Microsoft

           Apple OSX: an operating system by Apple Computers

           Ubuntu: an open source (freely available) operating system

—  Points to Remember

The speed of a CPU is measured in Hertz (Hz).

The speed generally corresponds to the number of actions the CPU can perform every second.
1 Megahertz (MHz) is 1,000,000 (1 million) Hertz

1 Gigahertz (GHz) is 1,000,000,000 (1 billion) Hertz

A typical, modern, fast CPU runs at around 2.8GHz. That means it can perform almost 3 billion actions every second! Top↑

 
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