A computer is a machine that is used to store and process data electronically Computer Definition.

COMPUTER COMPONEN

TS

A computer is a machine that is used to store and process data electronically

Computer Definition

Types of computer: 1- Personal Computer2- Network Computer3-laptop computers4-PDA5-Mainframe

MAIN PARTS OF A PC

Computer components

Software Hardware

• Hardware:

- Pieces of equipment that make up a computer

system.

- These are the parts you can touch (although many

parts are contained within the computer’s case).

HARDWARE

1+23

memory

Brain

1+2

HARDWARE

1+2

Input devices

3

Output devices

Memory

Brain

1+2

Computer

Computer hardware

Storage devices

Output devices

Input devicesmemory

Central Processing

Unit

CPU

THE CENTRAL PROCESSING UNIT(CPU):

is the brains of the computer. All the "thinking", calculating and processing is done by the CPU.The CPU also control the transfer of information between the secondry and main memory The speed at which a CPU can process information is Known as its Clock Speed This is measured in megahertz (MHz) or gigahertz (GHz).

1 megahertz = 1 million cycles per second. 1 gigahertz = 1000 megahertz.

The CPU also incorporates :1. an Arithmetic Logic Unit (which performs the calculations

and logical operations within the computer) 2. and a Control Unit (which fetches, decodes and executes

data from the memory).

INPUT DEVICES: An input device is any device that is used to

supply information to a computer (as data or

for the selection of commands/menus/icons

etc)

INPUT DEVICES.

Touch screen

Electronic board

OUTPUT DEVICESAny devices that allows the result of

computer processing activity to be seen or heard

OUTPUT DEVICES:

Output device:

The screen:

CRT

LCD

Plasma

Plotter

Speakers

Data Show

Memory

(RAM) (ROM)

RAM (RANDOM ACCESS MEMORY) OR MAIN

MEMORY : •Random access memory is used in a PC to temporarily store

data when you are using applications.

•RAM is also used to store program instructions and feed

information to the CPU to process.

• RAM is not permanent, when you switch off the PC (or shut

down), the contents of RAM are lost or emptied (This is known

as volatile memory.)

ROM (READ ONLY MEMORY): •This is a special type of memory which contains all the

information the computer needs to switch itself on, check that all

its systems are

working and to tell the PC what things are plugged into it.

• It cannot be changed or overwritten by you, and stays the

same even when the PC is switched off.

•Storage drives are used to store and transfer data

files.

•After data is entered into a computer, it must be

saved as a file to preserve its contents after the

computer is switched off.

STORAGE DEVICES

Hard disk Drive:

•HDD Usually fixed inside the computer and

stores large volumes of data, which can be

accessed and retrieved quickly.

•A software application must also install

files onto the hard disk drive in order to run

.

•The access time of a HDD is measured in

milliseconds(msec)

Floppy disk drive:

A floppy disk drive is like a hard disk, but with

removable disks called floppies, floppy disks or diskettes.

Floppies

can be used to transfer small files from one PC to another (up

to

1.4MB) CD-ROM/DVD-ROM Drive :

CD-ROM (Compact Disk – Read Only Memory)

CD-ROM -> CD-R -> CD-RW -> DVD -> DVD-R

Other Types of storage devices??

A

Byte

1 1010011

Bit

Storage Capacity uses several terms to define the increasing amounts of data that can be stored

:the amount of storage space needed to hold either a 1 or a 0 in memory (binary numbering ) .This is the smallest unit of computer memory

bit

Equal to 8 bits , this is the amount of storage space

needed to hold one character

byte

bytes 1024 Kilobyte(KB)

1024 KB Megabyte(MB)

1024 MB Gigabyte(GB)

1024 GB Terabyte

COMPUTER PERFORMANCE The user can judge the performance of a

PC according to how quickly tasks are performed .

Factors determine the overall operating speed of a PC:The clock speed of the CPUThe Capacity of the RAMThe Capacity and speed of the HDD

Computer components

Software Hardware

SOFTWARE: - Operating systems, office programs and games are examples

of software.

- Software governs when and how various pieces of hardware

can be put to a variety of uses

Operating Systems software :

•Is the software that runs the computer

•Microsoft Windows is the operating system a lot of

people use.

However, there are other forms of Operating systems

software such as Unix, Linux, OS2, BeOS, OS-X

(MacOS) and so on

Operating system cannot run without the BIOS

(Basic Input Output System)

Common Applications Software

Word Processing: Example Microsoft Word

Spreadsheets:. Example Microsoft Excel

Database: Examples Microsoft Access

Presentation: Example

Microsoft PowerPoint

Web browsing

Applications Software must be compatible with the Operating

Systems

BIOS (Basic Input Output System)

Sara Turn on her computer and then open the word processor to write her homework : What are the steps taken by the computer to do this task in order:

Load MS word intothe RAM

Run the BIOS software from the ROM

the BIOS crries out the Power On Self Test(POST) read the OS files from HDD and copy them to the RAM

2

4

3

1

two or more computers connected together is called a network

COMPUTER NETWORK :

Local Area Network(LAN)

Wide Area Network(WAN)

less than one square kilometre is a LAN While any network covering more than one square kilometre is WAN .

THE INTERNET, INTRANET, EXTRANET Internet : a vast computer network .

Which allows users all over the world to communicate with each other .Connections to the internet are made by an

Internet service Provider (ISP) Intranet: Many medium to large

organizations now operate their own internal networks that provide similar functions to the internet

Extranet : an intranet or part of an intranet which can be accessed by certain external users by the internet.