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.