The Computer

---

AREA TO BE COVERED

1.Introduction

2.Types of Computers

3.Main parts of a Computer

4.Computer Software

5.Computer speed and Capacity

6.Data security

7.Computer Viruses

Introduction

The computer is a data and an information-processing and an information-accessing tool.

It accepts information or data from the outside world and processes it to produce new information. It also retrieves the stored information efficiency.

Hence, “The computer is an electronic device capable of accepting information, applying prescribed processes to the information, and supplying the results of these processes.”

A computer usually consists of input and output devices, storage, arithmetic and logical units, and a control unit.

vA Computer is simply defined as an electronic device which has the ability to accept data and process it to useful products (ie Information)

vWith a Computer, data and Information can be Processed, Stored, retrieved as well as Transferred.

vPrinciple characteristics of a Computer includes;

1.It responds to a specific set of instructions in a well defined manner.

2.It can execute a prerecorded list of instructions (a program.)

3.It can quickly store and retrieve large amount of data.

TYPES OF COMPUTERS

§Computers can be generally classified by size and power as follows; though there is considerable overlap.

1.Microcomputers

2.Mini-computers

3.Mainframe Computers:

4.Super-computers

Microcomputers

A Personal Computer (PC)  is a small inexpensive single-user computer designed for an individual user.

ØActual Personal Computers can be generally classified by size.

ØThere are two basic flavors of chassis designs, i.e. Movable and Immovable.

1.Immovable Computers are designed to fit comfortably on top of a desk. e.g. Desktop Computer

2.Movable Computers.These are computers which are designed to fit on the laps and hand held        devices

e.g. Laptop Computers, Palm held Computers

LAPTOP 

Is an extremely lightweight personal Computer enough to fit easily in a briefcase that can run on battery or mains power and can fit on the laps.

PALMTOP COMPUTER

 Is a small hand held computer used for limited office systems and Internet access. It uses a special pen for input.

ØA palmtop is also refers to Personal Digital Assistant, a handheld device that combines computing, telephone/ fax, and network features.

MAIN PARTS OF A PC

Generally, a Personal Computer has two major parts, i.e.

        1.Hardware and 

2.Software.

1.HARDWARE

ÚHardware is simply defined as any physical component of a Computer system.

ÚHardware is further divided into five categories, i.e. Input device, Processing device, Output device, Storage device, Communication Devices 

  Examples of Computer Hardware

MONITOR-Displays the result of the process

    More Computer Hardware

Input Device

ÚIs a Computer component which is used to feed data and information into a Computer system.

Examples of input devices; Keyboard, Mouse, Scanner, Digital Camera, Microphone, Touch pads, Joystick, Webcam, Light pen e.t.c.

Processing Device

Is a Computer component that used to manipulate data in a Computer system.

Example. Central Processing Unit ((CPU)),

THE  CPU

The CPU has two major parts 

                            -the ALU(Arithmetic Logic Unit) and 

    -the CU(Control Unit).

Control Unit (CU), 

Is the nerve center of the computer, and controls activities of all units including the CPU.

-This Unit has the following functions:

•It fetches the instructions and data from the main memory

•Decodes instructions and interpret them.

•It issues the control signals to all other units to perform their respective required functions.

Arithmetic Logic Unit (ALU)

This unit controls all the arithmetic  and Logical operations such as:

-Arithmetic Operations

  •Addition (+)

      •Subtraction (-)

        •Multiplication (*)

•Division (/)

-Logic Operations

      *IF(
*SUM(
         *AVERAGE(

HIERARCHY OF OPERATIONS

-The order or priority in which the arithmetic operations are performed in an arithmetic statement is called the hierarchy of operations.

 The Hierarchy of arithmetic operations is as follows

Priority Operators

                                      1.   Parentheses—All parentheses are evaluated   first

2.   Division & Multiplication

 3.  Addition and Subtraction.

OUTPUT DEVICE

vIs a Computer component which used to display the processed information to the user.

vExamples; Monitor, Printer, Plotter, Speaker, Projection device e.t.c.

STORAGE DEVICE

Storage device (Secondary Memory device)

ÚIs a Computer component that used to store information permanently for future use.

ÚExample; Floppy Disk (Diskette), Hard Disk, Compact Disk (CD-ROM, CD-R & CD-RW), Digital Versatile Disk (DVD), Flash Disk, Tape Backup e.t.c

COMMUNICATION DEVICES

These are devices responsible for the connectivity of two or more computers for the purpose of sharing resources.                                                 E.g.

1.NIC- Network Interface Card

          2.Modem (Modulator/Demodulator)

DISK DRIVES

Is simply described as a component that used to read/ write data from/ into a storage device.

Examples;

                                           1.Floppy Drive i.e. 3½ Floppy (A:)

                                                                                  or 5¼ Floppy (B:)

                                                  2.Hard Disk Drive i.e. Local Disk (C:)

                                                                   3.Compact Disk Drive i.e. CD Drive (D: or E:)

                                                       4.Flash Drive i.e. Removable Disk (F:)

•

MEASURING MEMORY CAPACITY

vIt is important to realize that the term Digital Computer refers to the fact that ultimately the Computer works in Binary Number system ( i.e. 0 and 1) where humans work in Denary Number system (i.e. 0 – 9).

vHence the measurement of Memory capacity of a storage device is Bits (i.e. BInary digiTS).

                   1.    8 Bits = 1 Byte = 1 Character

          2.     1024 Bytes = 1 Kilobyte.

     3.    1024 Kb = 1 Megabyte

    4.    1024 Mb = 1 Gigabyte

     5.    1024 Gb = 1 Terabyte.

Communication Devices

These devices enables the computer to communicate to one another. Eg Modem (Modulator/Demodulator), Network Interface Card (NIC)

MODEM

A modem is a bridge between digital and analogue signals, and therefore provides an interface between computer (digital) and telephone (analogue) systems.

We use a modem to connect PCs to the ordinary telephone network: ie the Public Switched Telephone Network(PSTN).

MEMORY

-Types of Memory

                                        1.Random Access Memory(Main memory)(RAM);

  2. Read-Only Memory (ROM);

3. Processor cache memory.

MAIN MEMORY (RAM)

This type of memory can be both read from and written to, and any location can be accessed independently (this is why it is called Random Access Memory). This is the ordinary memory used for storing programs and data.

RAM is volatile: it looses its contents when the power to the PC is switched off, unlike the ROM which is Non-Volatile

Functions of the Main Memory:

-It stores program instructions and data as long as the power of the computer is on.

-It stores instructions awaiting to be processed

-It store instructions currently being processed

-It stores data awaiting processing

-It stores data currently being processed

-It stores intermediate results of processing

-It stores data awaiting output

READ-ONLY MEMORY(ROM)

This memory stores the basic that a computer executes when it is switched on, these instructions are programmed by the computer manufacture.   

   The common user need not change anything there.  Normally computer memory is temporary but this is maintained by long life battery that outlives the life span of the computer itself (CMOS BATTERY).  Some of the operations controlled by ROM include the Power On Self Test (POST), BOOTING procedure (loading of an operating system) etc.

Review Questions:

1.Why do you think that it is necessary for users to save data into secondary storage on a regular basis, as well as prior to switching off the power to the computer?

2.SOFTWARE

vIs simply described as a set of instructions which tells the Computer what and how to do.

vGenerally, there two major types of software,

1.  System Software

          2.  Application Software.

System Software

                                 -System Software is Divided into two types:

                      1.Operating System Software

2.Utility Programs

1.Operating System Software

vIs the type of software which designed to control all actions which are taking place in the Computer. E.g. All actions of Hardware.

vIt is the program which loads automatically when you start your Computer.

vExamples; Unix, Linux, Windows 3.1, Windows 95, Windows 2000, Windows XP, Vista, Windows 7.

Uses of the operating system software

-Controls all communications with the peripherals

-Enables the CPU to control more than one program at a time.

-Communicates with the operator or user.

-Management of the computer resources.

2.Application software.

Application software is developed for specific jobs.  They performs useful work on general purpose tasks such as; word processing, graphics, spreadsheet, etc.

There are two types of Application Software

1.General Purpose Application Software

 2.Specific Purpose Application Software

DATA SECURITY IN A COMPUTER

1.BACKUP: Is the process of storing data in external device. It is VITAL that you take regular backups of the information that is stored on the Computer due to the fact that if the Hard disk stops working one          day, you could loose all the data stored in your PC.

2.PASSWORD: If your Computer has a password that prevents other users from accessing it, then do not give this password to anybody else, do not write on a card and prop or hide on the underside of your         desk. (Make sure you don’t forget your Password.

3.SWITCHING OFF A PC: You must follow the proper way to switch off a computer.

4.UPS. Un-interruptible Power Supply is a device that you can attach to your Computer that will guard                               against power cuts.

COMPUTER VIRUSES

ÚVirus is a small program (Software) that hide itself on your disks designed by people for malicious purposes.

ÚSince virus hide on a disk, when you access that disk the virus program will start and infect your Computer.

To protect your Computer from Virus infection, you should install Virus-checking (Antivirus) program in your Computer. Also keep your virus monitoring software up to date.

Examples of Antivirus software includes; -MacAfee

                                                                 -Norton

                                                                 -DR Solomon, 

                                                                 -e-scan, 

                                                                 -AVG e.t.c.

Virus can spread from one Computer to another either via the use of infected diskette or over a Computer network.

OPERATING SYSTEM

Operating systems Concept

The operating system (OS) programs are system software that manages the basic operations of computer

TYPES OF OPERATING SYSTEM

Real-time Operating System

used to control machinery, scientific instruments and industrial systems.

Single User, Single Task OS

As the name implies, this operating system is designed to manage the computer so that one user can effectively do one thing at a time. Eg Palm OS for Palm handheld computers is a good

Single User, Multi-tasking OS:

This is the type of operating system most people use on their desktop and laptop computers today.

Eg Linux, Unix, Windows, Macintosh OS.

Multi-user OS

A multi-user operating system allows many different users to take advantage of the computer's resources simultaneously

FUNCTIONS OF OPERATING SYSTEM

-managing resources,

What is a resource?

-providing user interface,

-running user applications 

-Managing file storage

-Provides protection and security.

WINDOWS BASICS

-What is a Window ?

-What is Windows?

                                              -What is the Difference btn a window and windows?

• A  Window is  a rectangular box that appears when a program  is opened.
• Windows is a type of Operating System developed by Microsoft corporation.

Versions of Windows  operating system

 Windows 3.1

Windows 95

Windows 98

    Windows 2000

                                             Windows Millennium Edition (Windows ME)

Windows Xp

     Windows Vista

Windows 7

SWITCH ON A COMPUTER

1.Identify Power buttons for System Unit and that of Monitor.

2.Switch ON the Power button for System Unit followed by that of Monitor.

3.Wait for Operating System to be loaded in RAM

                 NOTE:

ØYou might be required to choose OS you want.

ØMake sure all cables are well connected.

ØYou might be required to LOG IN by providing Username and Password given to you by System Administrator.

A.USING COMPUTER & MANAGING FILES

1.WINDOWS SCREEN

ÚA Windows screen is referred to a Desktop.

ÚA Desktop contains various icons and Taskbar

                 ICON

ÚIs any object that can represent a file, a folder, a program or a drive.

ÚThe main icons on Desktop includes; My Documents, My Computer, My Network Places, Recycle Bin and Internet Explorer.

2.TASKBAR

ÚIs simply a bar that lies at the bottom of the Desktop.

ÚIt displays Start button, Quick launch, Running application and System tray.

1.WORKING WITH MOUSE

ÚThe following are the terms used when working with a Mouse.

1.POINT: Means moving a mouse pointer over the object.

2.CLICK: Means pressing left mouse button once. This will select (Highlight) the object.

3.DOUBLE CLICK: Means quickly pressing the left mouse button twice. This will open the object.

4.RIGHT CLICK: Means pressing right mouse button once. This will display a Pop up menu.

5.DRAGGING: Means moving an object to another location using mouse.

6.THE SYSTEM PROPERTIES SCREEN

-Right click on “My Computer” icon

-Click on “Properties” command

•Note: A System Properties dialog box will appear. Under General tab you will see the information about your Computer, Example; Type of Operating System, Size of RAM, Type of Processor and Clock speed.

Click on “Ok” when you finish.

2

.FILES AND FOLDERS

A.FOLDERS/ DIRECTORIES

ÚA Folder is an electronic container that stores files.

a)Creating a Folder on Desktop

i.Right click on a blank area of the Desktop

ii.Highlight on “New” command.

iii.Click on “Folder” option

iv.Type folder’s name

v.Press “Enter” key

b)Creating Folders in other locations.

i.Open the location you wish to create a new folder. E.g. Drive (C:)

ii.Right click on a blank area.

iii.Select “New” command

iv.Click on “Folder” option

v.Type a name of your folder

vi.Press “Enter” key

•Note: If the location is one of the drives, start by opening  My Computer, then open the drive.

c)Creating a Subfolder

i.Open a Parent (Main) folder.

ii.Right click on a blank area.

iii.Select “New” command

iv.Click on “Folder” option

v.Type a new name.

vi.Press “Enter” key

Note: A Subfolder is a folder that stored within other folder.

    A Parent folder is a folder that stores subfolders.

B.FILES

ÚA File is simply the collection of related information stored under one name.

ÚYou can create a file by using any application program.

ÚA file is identified using three factors i.e. File name, File location and File extension (File type)

ÚFile extension consists of three letters, separated from the file name by a period (.).

 Example; Utandawazi.doc, Maisha.rtf, Mazingira.txt, Pension.xls, Frag.jpg e.t.c.

 ð.doc – document files (Microsoft word)

 ð.rtf – rich text format files (WordPad application)

 ð.xls – Excel files (Microsoft Excel)

Creating a File.

i.Open the program you wish to create a file.

ii.Type (Enter) your information (i.e. Data)

iii.Save your file.

ðOpening a Simple Editing Program

i.Click on “Start” button.

ii.Select “Programs” command.

iii.Select “Accessories” option.

iv.Click on the program you want. E.g. Notepad, WordPad e.t.c.

ðWorking with a Keyboard.

vThe keys in a keyboard are divided into several categories as follows;

               i.Function keys: Used in special operations. E.g. F1 – F12

               ii.Numerical keys (Keypad): Used to type numbers, operators e.t.c.

               iii.Character keys: Used to type letters, numbers, symbols e.t.c.

øWorking with keyboard…

i.Special keys: Used for special purpose

 a.Space bar (Long) key: Used to provide a space between words during typing.

b.Enter (Return) key: Used to moves cursor to a second line.

 c.Caps Lock key: Used to switch between uppercase and lowercase.

d.Shift key: - Used to switch between uppercase and lowercase when Caps key is OFF. Also is used to access a second character when a key has two character

e.Backspace key: Used to delete (erase) characters at the left side of the cursor position.

f.Cursor control keys: Used to control movements of cursor.

                   g.Arrow keys: Used to move cursor one character to the direction of arrow.

                   h.Home key: Used to move cursor direct to the beginning of line

               i.End key: Used to move cursor to direct to the end of line.

                    j.Delete key: Used to erase (delete) characters at the cursor position.

1

ðSaving a New file.

i.Click on “File” menu

ii.Click on “Save” or “Save As…” command

 Note: You will see a Save As dialog box.

iii.Select the location, under Save In text box. E.g. Desktop, My Document, 3 ½ Floppy (A:)

iv.Type a name of the file, under File Name text box.

v.Specify the file extension, under File type text box.

vi.Click on “Save” button.

ðOpening an Existing (Saved) file.

i.Click on “File” menu

ii.Click on “Open” command

 Note: You will see a Open dialog box.

iii.Select the location, under Look In text box. E.g. Desktop, My Document, 3 ½ Floppy (A:)

iv.Click on a name of the file you wish to open.

v.Click on “Open” button.

ðEditing a file. E.g. Format Fonts.

1.Select the text you wish to format.

2.Click on “Format” menu.

3.Click on “Fonts” command.

 Note: Fonts dialog box will appear.

4.Select the options you want. E.g. Font, Font type, Font size, Font color e.t.c.

5.Click on “Ok” button.

ðSaving changes in existing file.

i.Click on “File” menu

ii.Click on “Save” command

 Or: - Click on “Save” icon on Standard toolbar.

 Or: - Press and hold down “Ctrl”, then press on “S” key. (i.e. Ctrl + S)

1.ORGANIZING FILES

ØWhen accessing a hard disk (whether it is a local or located on a network), Windows uses the system of drive letters to save as logical pointers to the different physical drives you have access to.

ØFrom each drive letter it is possible to access all of your files stored on that particular drive.

ØIf all of the files were held together in one place on each drive, the system would be very difficult to use because of sheer number of files involved.

ØTo help organize your files, you are advised to create folders to held divide and even sub divide the files stored within the various logical drives available.

2.THE WINDOWS EXPLORER

ðUsing Windows Explorer.

üWindows Explorer is the option that permits you to explore all aspects of your system using a hierarchical view.

ðOpening Windows Explorer

1.Click on “Start” button

2.Click on “Programs” command

3.Click on “Accessories” option

4.Click on “Windows Explorer”

 OR: Right click on “Start” button, then click on “Explore” command.

ðWindows Explorer Screen

ØThe Windows Explorer is split into two separate views. i.e. Left and Right windows.

ØThe left window refers to Folders pane; displays the folders and disk drives arranged in Tree format. To expand a tree click on a plus sign (+) where as to collapse a tree click on a minus sign (-).

ØThe right window refers to Contents pane; displays the contents of a selected item from the left window.

1.Managing Files and Folders using Windows Explorer.

1.Changing  icons View mode.

i.Right click on a blank area in contents pane.

ii.Select “View” command

iii.Click on the option you want. E.g. List e.t.c.

2.Changing icons Arrangement

i.Right click on a blank area in content pane.

ii.Select “Arrange Icons” command

iii.Click on the option you want. E.g. By Date.

3.Copying items within the same location

i.Right click on the item you wish to copy.

ii.Click on “Copy” command

iii.Right click on a blank area.

iv.Click on “Paste” command.

•OR;

i.Select the item you wish to copy

ii.Click on “Edit” menu, then click on “Copy” command

iii.Click on the blank area.

iv.Click on “Edit” menu, then click on “Paste” command

1.

4.Copying items in another location

i.Right click on the item you wish to copy.

ii.Click on “Copy” command

iii.Open the location you wish to place a copy.

iv.Right click on a blank area.

v.Click on “Paste” command.

•OR;

i.Select the item you wish to copy

ii.Click on “Edit” menu, then click on “Copy” command

iii.Open the location you wish to place a copy.

iv.Click on “Edit” menu, then click on “Paste” command

1.

5.Moving items in another location

i.Right click on the item you wish to move.

ii.Click on “Cut” command

iii.Right click on a blank area.

iv.Click on “Paste” command.

•OR;

i.Select the item you wish to copy

ii.Click on “Edit” menu, then click on “Cut” command

iii.Open the location you wish to place your file.

iv.Click on “Edit” menu, then click on “Paste” command

1

6.Removing items

i.Right click on the item you wish to remove.

ii.Click on “Delete” command

iii.Click on “Yes” button

•OR;

i.Select the item you wish to remove

ii.Click on “File” menu

iii.Click on “Delete” command

iv.Click on “Yes” button

7.Un-deleting items

i.Open the Recycle bin.

ii.Right click on the item you wish to recover.

iii.Click on “Restore” command

•OR;

i.Select the item you wish to recover.

ii.Click on “File” menu

iii.Click on “Restore” command

•Note: You can’t restore any item deleted from the Recycle bin or external storage device like Diskette

1

8.Renaming items

i.Right click on the item you wish to rename.

ii.Click on “Rename” command

iii.Type a new name

iv.Press “Enter” key

•OR;

i.Select the item you wish to rename

ii.Click on “File” menu

iii.Click on “Rename” command

iv.Type a new name

v.Press “Enter” key.

2.Multiple Selection technique

A.Continuous Selection

i.Select first item

ii.Press and hold down “Shift” key.

iii.Select last item, then release shift key.

B.Non-continuous Selection

i.Press and hold down “Ctrl” key

ii.Click on each item you wish to select.

3.Searching Files or Folders

i.Click on “Start” button

ii.Click on “Search” command

iii.Click on “For Files or Folders…” option

iv.Enter a filename or folder name on a text box provided

v.Click on “Search” button.

                                                                                                  

                                             

    ==========================E====N====D========================