IGCSE Information Communication Technology (ICT) Syllabus code 0417

Section 1:

Types and components of computer systems

Section 1

a. define hardware, giving examples; b. define software, giving examples; c. describe the difference between hardware and software; d. identify the main components of a general-purpose computer:

o central processing unit (CPU), o main/internal memory (including ROM and RAM), o input devices, o output devices, o secondary/backing storage.

e. identify operating systems, including: o graphic user interface (GUI), o command-line interface

f. identify different types of computer including: o personal computer (PC) or desktop o mainframe

What is a computer?

A computer is, at its most basic, a machine which can take instructions, and perform

computations based on those instructions.

Computers range from the very small to the very large. Some are capable of doing millions

of calculations in a single second, while others may take long periods of time to do even the

most simple calculations.

Based on Capacity, speed and reliability computers can be divided into the following

categories of computers:

Super computer

Mainframe Computer

Minicomputer

Microcomputer

Types of Computers

Super computer

A supercomputer is a computer which performs at a rate

of speed which is far above that of other computers.

The primary use for supercomputers is in scientific

computing, which requires high-powered computers to perform complex calculations.

Scientific organizations like NASA boast supercomputers the size of rooms for the purpose of

performing calculations, rendering complex formulas, and performing other tasks which

require a formidable amount of computer power. Some supercomputers have also been

designed for very specific functions like cracking codes and playing chess; Deep Blue is a

famous chess-playing supercomputer.

Mainframe Computer

These are computers used by large organizations like meteorological surveys and statistical

institutes for performing bulk mathematical computations. They are core computers which

are used for desktop functions of over one hundred people simultaneously. Since

mainframes are usually the most important computers in a company’s computational

arsenal, they are routinely protected by multiple layers of security and power backup, both

internal and external. mainframe computer

Mini computers

The Mini computers are a less bulky version of the mainframe computers. In times past, the

minicomputer was typically a standalone device that was ideal for use by small and mid-

sized businesses who needed more power and memory than

could be obtained with microcomputers, but did not have a

need for the resources provided by mainframes. More

recently, a minicomputer is thought of in terms of being a

server that is part of a larger network.

The Microcomputer

These are the most frequently used computers better known by the name of “Personal

computers”. This is the type of computer meant for public use. Other than Desktop

Computer the choice ranges as follows:

Personal Digital Computer

Tablet PC

Towers

Work Stations

Laptops

Hand Held Computer

Components of a Computer

CPU

The CPU or the Central Processing unit is the brain of the computer and the single most

important chip in the computer. Modern processors contain

millions of transistors which are etched onto tiny square silicon

called a die, which is about the width of a standard thumb. The

CPU performs the system's calculating and processing.

The speed at which a CPU processes is known as its Clock speed.

The speed of the CPU is measured in either Megahertz (MHz) or

more commonly now in Gigahertz (GHz). A 1 GHz CPU can carry out 1 billion instructions per

second!

Now days, CPU available in the market, have a clock speed of 3 GHz.

Arithmetic logic unit (ALU) is a digital circuit that performs arithmetic and logical operations.

The ALU is a fundamental building block of the central processing

unit (CPU) of a computer, and even the simplest microprocessors

contain one for purposes such as maintaining timers.

Main Memory

The main memory holds the program instructions and data. It

contains two types of memory chip, called ROM and RAM.

Input Devices

Input devices are used to put data and

instructions into a computer. Most common

input devices are keyboard and mouse. Click

here to go to Input Devices topic

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. Click here to go to Output

devices topic.

Secondary /backing storage devices

Secondary or backing storage is used to

store programs and data when they are

not being used

What is Software?

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.

that are coded by programming languages like C, C++,

etc.

"Software" is sometimes used in a broader context to

mean anything which is not hardware but which is used

with hardware, such as film, tapes and records.

Types of Software

System software

System software helps run the computer hardware and computer system. It includes:

device drivers

operating systems

servers

utilities

Programming software

Programming software usually provides tools to assist a programmer in writing computer

programs, and software using different programming languages in a more convenient way.

The tools include:

compilers

debuggers

interpreters

linkers

text editors

Application software

Application software allows end

users to accomplish one or more

specific (not directly computer

development related) tasks.

Typical applications include:

industrial automation

business software

computer games

telecommunications (i.e. the internet and everything that flows on it)

databases

educational software

medical software

Typical examples of 'software applications' are word processors, spreadsheets, media

players and database applications.

Utility Software

Programs that perform everyday tasks such as defragmenting a hard disc drive or performing a backup of data.

Difference between Hardware and Software

There are several differences between computer hardware and software. However, the

fundamental difference between hardware and software is that hardware is a physical

device something that you're able to touch and see. For example, the computer monitor

you're viewing this text on or the mouse you're using to navigate is considered computer

hardware.

Software is code and instructions that tell a computer and/or hardware how to operate. This

code can be viewed and executed using a computer or other hardware device. However,

without any hardware software would not exist. An examples of software is Microsoft

Windows, an operating system that allows you to control your computer and other programs

that run on it. Another example of software is the Internet browser you're using to view this

page.

To make it simple...

Hardware is the actual components that your computer is made of: ram, rom, motherboard,

modem, wireless chip etc. Software is any program that you load onto a computer: the

operating system (Windows, Lynix) games or applications.

Operating system

An operating system (commonly abbreviated to either OS or O/S) is an interface between

hardware and applications; it is responsible for the management and coordination of

activities and the sharing of the limited resources of the computer

. The operating system acts as a host for applications that are run on the machine. As a

host, one of the purposes of an operating system is to handle the details of the operation of

the hardware.

Functions of an operating system

Input/ Output control Handling Errors Allocating resources to programs Providing the user with an interface to control the computer Handling files stored on a backing store

Controlling the OS

Telling the operating system what to do requires a user interface that lets the user give instructions. There are two main types of user interface.

Graphical User Interface Command Line User Interface

Graphical User Interfaces

All operating systems do not look the same, MS Windows looks different from Mac OS X and they both look different from the GNOME desktop of some LINUX distributions.However these examples do have something in common. They are all Graphical User Interfaces or GUI's (pronounced gooey). These are designed to make operating the computer as easy as possible They provide

Windows Icons Menus Pointer

Collectively these features are known as WIMP.

The only one that might need explanations is 'Icons', these are pictures that represent something e.g. a text document icon on the desktop. This icon is not the document itself but it represents the document and when clicked will cause the document to be loaded.

Command Line Interfaces

Some operating systems have the option of a command line interface or a GUI, others only have a command line interface. A command line interface is not as easy to use as a GUI. Users have to type commands and there is no indication what commands are possible, so users have to know what they are doing! You can access the command prompt in MS Windows from the accessories folder in the programs menu.