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Storage Devices

Z Is the physical material on which a computer keeps data, instructions and information.

Z There are 2 types of devices storage :

- Magnetic Disks :

Use magnetic particles to store items on a disk’s surface. Three type of magnetic disks are Hard disks ,Floppy disks and Zip disks

- Optical Disks:

Optical discs store items by using microscopic pits ( indentations) and lands (flat areas) that are in the middle layer of the disc.

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Storage Devices

Z Hard disk drive HDD– this stores all your programs and data.

Z HDD stores huge amount of data, the capacity is measured by GB, the speed of HDD is called access time.

Access time is the time required by HDD to search and retrieve data.

Access time is measured by millisecond (msec)

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Other Storage Devices

Z Floppy disk drive – this stores smaller files.

Z Zip Drive, Uses zip disks which can store

either 100Mb or 250Mb of data, Can be internal or can plug into

a PC’s USB port

Z Flash Drives, Plug into a USB port, Typical storage – 28Mb, 256Mb,

512Mb,1GB-32GB.

Zip Drive Floppy Disk

Flash memory

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Note

Z Data is saved as magnetized dots on Magnetic storage medium.

Z Storage surfaces is divided into : Track an Sector.

Z Formatting: the process of preparing storage disk for use, it creates Tracks and Sectors.

Z When you format your disk, all data is erased and the disk will be as “ anew” one.

Track Sector

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Storage Devices

Z There are many different formats of optical discs exist today. CDs and DVDs

Z DVDs having a much greater storage capacity than CDs.

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Storage Devices

, CD –ROM : software and games are normally supplied on CD ROM disks. Information is read-only and cannot be changed.

CD capacity : 650MB (75 min of music).

, CR-R (Recordable): user can store data once .

, CD-RW (Re-Writable): allow user to save data many times.

, DVD ROM drive – these can be used to watch films etc.

, DVD-R (Recordable): used to save data once.

DVD capacity: 4.7GB (120 min video).

CD-

ROM

CD-

R

CD-

RW

DVD

DVD-

R

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The System UnitZ System Unit is a case that

contains electronic components of the computer

Z It can be a tower case or desktop case.

Z The main circuit board of the system unit is the motherboard.

Z motherboard contains complex electronic circuits and silicon chips.

Z All the computer components plug into the motherboard either directly into slots or by cables.

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The System Unit

CD-ROM Drive:Read information and write on CD, read from DVD.

Floppy disk drive:Read and write information From floppy disk.

On/ Offswitch

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The System Unit

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Removable Storage Comparison

Device Capacity

Floppy disk 1.44Mb

Zip 250Mb

Flash drives 256Mb

CD 650Mb

DVD 4.7Gb

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Computer Performance

, The clock speed of the CPU (measured in MHz, GHz).

, The capacity of RAM installed (measured in MB, GB).

, The capacity and speed of HDD (Hard Disk Drive).

, The number of application running.

Four main factors will determine the Performance of computer:

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Software Components

Computer

Hardware

CPU

Memory

Storage Devices

Input Unit

Output Unit

Software

Operating System

Application

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Operating System (OS)

Z OS: A special computer programs that organise and control a computer., Provides an interface so that the user can communicate with the computer., Communicates between software and hardware devices., Organises the storage and retrieval of information.

, Manages the smooth running of programs running in RAM by allocating the required resources.

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The BIOS (Basic Input/Output System)

Z The operating system cannot run without the BIOS.Z It is a basic SW that is stored in ROM.Z The BIOS make sure that the hardware operates

properly. And it loads the operating system.Z Also it records basic information about the PC.Z Usually it configured by the manufacturer.Z No user intervention is usually required.

What happens when computer boots up??

Z When computer is switched on, BIOS carries out (POST) – Power On Self Test and do boot-up operation.

Z Boot-up operation has 2 main functions:, Ensure that all hardware is running ,CPU and memory are

functioning correctly., Load the operating system (OS) from HDD to RAM.

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Example of Operating Systems

Z Microsoft Windows: Windows95, Windows Me, Windows XP, Windows Vista.

Z MS-DOS created by Windows but text-based

Z Macintosh (MacOS) was created by Apple.

Z Linux is a popular alternative open-source OS.

Z Unix is another OS used in companies or universities.

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User interface

Z You interact with software through its user interface.

Z The user interface controls how you enter data and instructions and how information is displayed on the screen.

Z 2 types of user interfaces are , Command-line interfaces., Graphical user interfaces

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Command-line interfaces

Z User types commands or presses special keys on the keyboard to enter data and instruction.

Z Its difficult to use because they require exact spelling, grammar and punctuation

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Graphical User Interface (GUI)

Z Enables users to click and point at icons and menus on screen, instead of typing in computer commands

Icon

Menu

Keeping Up to date

Z The latest versions of operating system will be updated regularly.

Z New versions often have improved security and have fix bugs that may have present in older versions.

Z And they will often have attractive new features too.Z Between versions of the operating system, the

manufacturer regularly release updates and service packs.

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Keeping Up to date

Service packs:

Z A collection of updates, fixed for your operating system.Z It contains new drivers for many computer components. Z Could be supplied on a CD or downloadable from the

internet.

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Application Software

Z Application software: is a computer programs designed for a specific purpose.

Z Application software is separate from the operating system but must be compatible with it in order to be able to operate.

Z Each application software is suited for special purpose…. See following example.

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Examples of Application SoftwareUses Example Application

Format text, write letter Microsoft Word Word Processor

Organize numbers in tables and do calculations

Microsoft Excel Spreadsheet

Stores large data that can be questioned

Microsoft Access Database

Design presentation with text, image, sound, video.

Microsoft PowerPoint Presentation Tools

Design large pager like poster and catalog

Microsoft Publisher Desktop Publishing

View and organize email Microsoft Outlook Express E-mail

Access information on the internet.

Microsoft Internet Explorer Web browsing

Design graphics Photoshop/ CorelDraw Graphics23

Did you see this message???

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Problem Solving

Problem reason

Hardware

No printout

Software

Application not respond

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Common error indicators

Z No display on the screen.

Z Error messages on screen.

Z Flashing lights on printer.

Z No printer output.

Z No mouse cursor.

Z Bleeping sounds from system unit.

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Resolving problems

Z Basic checks:, Power supplies, External connections, Supplies of consumables

Z Manufacturer support

Z Manuals

Z Windows Help and Support Centre

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Other considerations

Z Error reporting

Z Automatic System Updates

Z Device drivers

Z Backups

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Understanding your computer setup

Z Help and Support Centre

Z Control panel:

, Change the computer’s date and time

, Change the volume settings, Check which printers are

installed, Check which is the default

printer

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Other system information

Z Networking information

Z Performance and maintenance information, Managing active applications

Z System properties, Storage areas

System Development

Analysis •Perform by “system analysts”.•Meet Project members, set objectives, write specifications.

Programming •Perform by “programmers”.•Write the program using programming language.

Testing •Perform though development to correct system “bugs” and faults.•Next test performs by users who can use the system (Beta testing).

Documentation •Written the finished system.•2 levels: technical operation for future development, user guides.

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System development cycle is a set of activities used to build an information system.

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Look at this picture..

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Computer Network

Network:

Connecting 2 or more computers together.

Advantages of computer networks:

Z Share resources (data, applications, peripherals like printers& scanners).

Z Provide high performance.Z Enhance system security (authorized

access giving username and password).

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LAN & WAN

LAN:

(Local Area Network)

Computers that linked together by cables or wireless within building or close area covers less than one square kilometer.

WAN:

(Wide Area Network)

Computers linked up over longer distance by telecommunications network that covers more than one kilometer distance.

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LAN & WAN

LAN:(Local Area Network)

Computers that linked together by cables or wireless within building or close area covers less than one square kilometer.

WAN:(Wide Area Network)

Computers linked up over longer distance by telecommunications network that covers more than one kilometer distance.

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WANLAN

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WANLAN

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Server & Client

Server:

it is the main computer in the network which stores all core data and controls access to HW, SW and other resources on a network.

Client:

Peripherals PCs which allow users to interface with the server and access data.

ClientsServer

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Telephone Network

Z Advanced telecommunications means that computers can

be linked to telephone systems to produce WAN.

Z To link computers to telephone line you need a modem to

transmit data from digital signal to analogue signal and

back.

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Digital and Analogue signals

Digital:Z Digital data is transmitted as a

series of digits (0 or 1).Z Data in digital form can be

transmitted more accurate and quickly.

Analogue:Z Analogue transmission transfer

data as electromagnetic wavesZ Data in analogue form

transmitted slower and corrupted.

0

1 1 1 1 1 1

0 0 0 0

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What is a Modem??

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Modem

Modem (Modulator/demodulator):

A device that converts a digital signals with in computer to analogue signal to pass along standard telephone line “dial up” internet connection.

Transfer rate is the speed of modem over telephone line. “Dial up” connection is now replaced by “Broadband”

which use data line instead of telephone line.

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Types of Network

Properties Types of Network

Basic systems, analogue, dial-up connection, slow transfer rate.

Public Switch Telephone Network

PSTN

Faster than PSTN, no modem needed, no dial-up.

Integrated Services Digital Network

ISDN

Faster than PSTN and ISDN but, special modem required, no dial-up.

Asymmetric Digital Subscriber Line

ADSL

Faster than telephone access, but only available in highly populated area.

Cable

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The Internet

Internet:Z The internet is a computer network, which allow user all

over the world to communicate.

WWW (World Wide Web):Z It is the collection of information that can be accessed by

internet, this information stored in web sites (web pages).

Internet is not the same as WWW

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Search engine

Z Is a site connected to a powerful database, you can search for any information using keywords.

Z Examples: Google, Yahoo.

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Intranet & Extranet

Intranet:Z Internal network that

operate similar as internet, but can be accessible only within organization.

Z Web pages containing company information and forms can be downloaded.

Extranet:Z Part of intranet can be

accessed by certain external user via internet.

Z Access this part of intranet is controlled by username and password.

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E-mail

E-mail (Electronic mail):Z Sending message from one computer to another via

electronic mail box using email address.

Attachment:Z An electronic files that you can send with email message

like: image, documents, presentations.

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What you need to send/ receive emails?

Hardware:Z Modem.Z telephone line.

Software:Z Messaging software (Outlook).Z ISP (Internet Service Provider) who provide the connection

to the internet through servers.