Lecture 2- Modern Computer Systems

7/29/2019 Lecture 2- Modern Computer Systems

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INTRODUCTION INFORMATION

TECHNOLOGY

Modern computer

systemslecture 2


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Objectives

What makes up a computer system

Various types of computers

Components of a computer system

Software (makes the computer useable)

Data representation in computers

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What is a computer?

Computer: An electronic system that can beinstructed to accept, process, store, and present

data and information.

Computers come in three most commonsizes:

Super computers

Mainframes

- Micro computers



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Computer shapes/sizes contd..

Mainframe computers are not as powerful,

generally not as large, and typically not as

expensive as super computers.

Mainframe computers are used in large

organizations where data processing iscentralized and there is need for this

data/information to be shared by staff in

different departments or different geographical

locations.

These computers can house large volumes of

data and can process 1 billion instructions per

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Computer shapes/sizes contd..

Microcomputers: The smallest and leastexpensive category of general-purpose

computers is called micro computers or

personal computers.

They may be sub-divided into five classifications;

Desktop Computers

Notebook Computers/Laptop Computers

Tablet PCs

Personal Digital Assistants

Palm PCs



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Computer system

Computer System: A computer and all thehardware interconnected with it.

Hardware

Software/ProgramsData/Information

People

Procedures



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Components of a computer system



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Computer

Hardware

(Physical Parts)

Software

(Instructions/ Programs )

Input Devices

Output Devices

Storage(Secondary Memory)

System Software

ApplicationSoftware

Mouse, Keyboard,Scanner, etc

Monitor,Speakers

Hard Disk drive, Floppy disk, FlashDisks, Compact Disk

Operating System Software

Processor(CPU)

Database S/W

Graphics S/W

Ms Word

MS-Windows xp, Linux, Unix

Data &Users



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Components of a computer

system : Hardware

A computer's hardware consists of electronicphysical devices; the parts you can see and

touch.

The term "device" refers to any piece of

hardware used by the computer, for example a

keyboard, monitor, modem, mouse, etc.



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Examples of hardware



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Classifications of hardware

Hardware can be classified into four categories i.e.input devices, processors, output devices and

secondary storage devices.



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Hardware contd..

input devices

Input: The data or information entered into acomputer or the process of entering data or

information into the computer for processing,

storage and retrieval, or transmission. Keyboards

Mouse

Touch screen

Digital camera

Scanner

Bar code reader



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Hardware contd..

Processor/Central Processing Unit (CPU):A set of electronic circuits that perform thecomputers processing actions.

Output Devices

Output: The results of inputting and processingdata and information returned by the

computer, either directly to the person using

the system or to secondary storage.

Printer

Speakers

Monitor

Microphone Pro ectors 3/2/2013 15Charles Asiimwe


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Hardware contd..

Secondary Storage Devices Secondary Storage (Auxiliary Storage):A

storage medium that is external to the

computer, but that can be read by the

computer; a way of storing data andinformation outside the computer itself.

floppy Diskettes

Flash disks

External hard drives

Zip disks

CD-ROM disk: Short for compact disk read only memory,an optical storage medium that permits storage of large amounts of

information. CD-ROM disks canonly be written to and cannot be3/2/2013 16Charles Asiimwe


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system : Software

Software is a general term for a set ofinstructions that controls the computer and

tells it what to do.

A Program is a set of instructions that directsa computer to perform certain tasks and

produce certain results.

Software controls the operations of a

computer, and without it, a computer is just adump machine.



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Software contd..

Software are of two types;

System software

Application software

System softwareSystem software is computer software

designed to operate the computer hardware

and to provide and maintain a platform for

running application software.

One major type of system software is the

operating system (OS). All computers require

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Software contd

The OS defines the interface between thecomputer user and the computer.

It also monitors the way the other software

use the hardware. It controls and ensures that the computer

operates in the way intended in a

systematic, reliable and efficient manner.

Common operating systems includeWindows XP, Vista, Windows 7, and Unix

(Linux these days) .



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system : People

Users and Creators of IT Applications User (End User): The people who use IT in their

jobs or personal lives

Programmer/Analyst: A person who has jointresponsibility for determining system requirements

and developing and implementing the systems.

Computer Engineer: An IT professional who

designs, develops, and oversees themanufacturing of computer equipment.

Systems Engineer: An IT professional who installs

and maintains hardware



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Procedures contd



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Procedures contd

Operations Procedure: A procedure thatdescribes how a computer system or

application is used, how often it can be used,

who is authorized to use it, and where the

results of processing should go.

Backup Procedure: A procedure that describes

how and when to make extra copies of

information or software to protect againstlosses.

Recovery Procedure: An action taken when

information or software must be restored.



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Procedures contd

Security Procedure: A procedure designed tosafeguard data centers, communications

networks, computers, and other IT

components from accidental intrusion or

intentional damage.

Security Software: Software that is designed

to protect systems and data.

Development Procedure: A procedure thatexplains how IT professionals should describe

user needs and develop applications to meet

those needs.



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Representing

Dataand Information



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How computers represent Data

Binary Numbers

The Binary Number System

Bits and Bytes

Binary Codes



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The limitation of a computer to understand the

human languages necessitated the changing

of data to binary form, known as coding ofdata.

In other words, to make communicationpossible between a computer and man, data

must be coded in a form understandable to

the computer.

The information also supplied by thecomputer as a result of processing must be

decoded in the form understandable to theuser.



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Binary codes

ASCII is the most common binary-code whichstands forAmerican Standard Code for

information Interchange.

In ASCII, each character consists of eight bits

(one byte) of data. ASCII is used in nearly all

personal computers.



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Memory measurements

A bit is a binary digit, the smallest unitmeasurement of data on a computer.

A bit can hold only one of two values: 0 or 1,

corresponding to the electrical values of off or

on, respectively. Because bits are so small, you rarely work

with information one bit at a time. Bits are

usually assembled into a group of eight to

form a byte.

A byte contains enough information to store a

single ASCII character, like "h".



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Memory measurements

1 Kilobyte (KB) 1,024 bytes

1 Megabyte

(MB)

1,048, 576 bytes

1 Gigabyte

(GB)

1,073,741,824 bytes

1 Terabyte (TB) 1,099,511,627,776 bytes

1 petabyte (TB) 1,125,899,906,842,624

bytes



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Memory measurements

Computer storage and memory is often

measured in megabytes (MB) and gigabytes

(GB). A medium-sized novel contains about

1MB of information. 1MB is 1,024 kilobytes, or

1,048,576 (1024x1024) bytes.

Lecture 2- Modern Computer Systems

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