2. WHAT IS A COMPUTER
A computer is an electronic device, operating under
the control of instructions stored in its own memory
that can accept data (input), process the data
according to specified rules, produce information
(output), and store the information for future use.
3. FUNCTIONALITIES OF A COMPUTER
• Any digital computer carries out the following functions:
Takes Data as Input
Store Data on its memory and use them when required
Process and convert data into information
4. CHARACTERISTICS OF A COMPUTER
• Speed-The computer can process data very fast, at the rate of
millions of instructions per second.
• Accuracy: Computer provides a high degree of accuracy.
• Diligence: When used for a longer period of time, the computer
does not get tired or fatigued.
• Storage Capability.
• Ability to Multitask.
5. TYPES OF A COMPUTERS
• Mainframe Computers: These are the largest and most powerful of
computers. The biggest of these are sometimes called
Supercomputers. Mainframes are usually only found in large
corporate institutions, research organisations, government
ministries and tertiary academic institutions.
• Workstation : A powerful, single-user computer. A workstation is like
a personal computer, but it has a more powerful microprocessor and a
6. TYPES OF COMPUTERS CONT.….
Personal Computer: Personal computers or PCs for short are the type of
computer that most users are familiar with. Because they are usually found on
users desks, they are also sometimes called desktop computers.
Laptop: Laptops are similar to personal computers except that they comprise
an integrated unit. Instead of a separate monitor, the lid contains a screen.
The keyboard is built into the base.
Persona Digital Assistant: The PDA is the smallest of all computers. Their
main task is to maintain a diary and keep contact lists.
7. COMPONENTS OF COMPUTER
• Computer hardware is the collection of physical elements that
constitutes a computer system.
• Computer hardware refers to the physical parts or components of a
computer such as the monitor, mouse, keyboard, computer data
storage, hard drive disk (HDD), system unit (graphic cards, sound
cards, memory, motherboard and chips), etc. all of which are physical
objects that can be touched.
9. WHAT IS AN INPUT?
What is an Input?
• Input is any data and instructions entered into the memory of
• Data is a collection of unprocessed text, numbers, images,
audio and video. Once the data is in memory, the computer
interprets and executes instructions to process the data into
10. WHAT IS AN INPUT DEVICE?
• An input device is any hardware component that allows users to enter data and
instructions (programs, commands and user responses) into a computer.
Types of Input Devices
• Tracker balls
• Touch pads
• Web cams
• Digital cameras and Voice recognition
11. INPUT DEVICES CONT’D…
• A keyboard is an input devices that contains keys users press to enter data or
instructions into a computer. It has evolved over the years. The keyboard is built into
laptop computers but is a separate item if used with a Desktop computer. They can be
connected vial cables or may be wireless.
12. INPUT DEVICES CONT’D…
• Mouse – when using an operating system, such as Microsoft windows, you use the
mouse to select drop down menus, to point and click on items, to select items and to
drag and drop items from one place to another.
13. INPUT DEVICES CONT’D…
• Scanner – allows you to scan printed material and convert it into a file format which
may be used within the PC. You can scan pictures and then manipulate these inside the
PC using a graphics application of your choice.
14. INPUT DEVICES CONT’D…
• Tracker ball – is like an upside-down mouse. To move the pointer using a trackball, you
rotate the ball with your thumb, fingers or the palm of your hand. In addition to the
ball, a trackball usually has one or more buttons that work just like a mouse buttons. It
requires frequent cleaning because it picks up oils from fingers and dust from fingers
and dust from the environment.
15. INPUT DEVICES CONT’D…
• Touch pads – is a small, flat, rectangular pointing device that is sensitive to pressure
and motion. To move the pointer using a touchpad, slide your fingertip across the
surface of the pad. Some touchpads have one or more buttons around the edge or the
pad that work like mouse buttons.
16. INPUT DEVICES CONT’D…
• Joystick – is a vertical lever mounted on a base. You move the lever in different
directions to control the actions of the simulated vehicle player. The lever usually
includes buttons called triggers that you may press to activate certain events.
17. INPUT DEVICES CONT’D…
• Web cams – ever since it was invented, the web has become increasingly interactive.
You can now use a small digital movie camera (a web cam) mounted on the PC
monitor to allow two-way communication involving not just text communication but
sound and video communication as well.
18. INPUT DEVICES CONT’D…
• Digital cameras – allow users to take pictures and store the photographed images
digitally, instead of on traditional film. These pictures can easily be transferred to your
computer and then manipulated within any graphics programs which you have
installed on your computer.
19. INPUT DEVICES CONT’D…
• Voice input – is the process of entering input by speaking into microphone. The micro-
phone maybe a stand-alone peripheral that sits on top of a desk, or built in the
computer or device, or in headphones or earphones.
20. WHAT IS AN OUTPUT?
• Output is data that has been processed into a useful form. Computer process data
(input) into information (output). A computer generates several types of output,
depending on the hardware and software being used and the requirements of the user.
• Users view output on a screen, print it, or hear it through speakers, headphones, or
earphones. Monitors, notebook, computers, Tablet PCs, PDAs, and smartphones have
screens that allow users to view documents, web sites, email messages, and other
types of output.
21. OUTPUT/DISPLAY DEVICES
• A display device is an output device that visually conveys text, graphics and video
information. Information on a display device, sometimes called soft copy, exists
electronically and appears for a temporary period.
• Display devices consist of a screen and the components that produce the information
on the screen. Desktop computers typically use a monitor as their display device.
22. OUTPUT/DISPLAY DEVICES CONT’D…
• Data Projectors – is a device that takes the text and images displaying on a computer
screen and projects them on a large screen so an audience can see the image clearly.
23. OUTPUT/DISPLAY DEVICES CONT’D…
• An audio output device is a component of a computer that produces music, speech
or other sounds such as beeps. Three commonly used audio output devices are
speakers, headphones and earphone.
24. OUTPUT/DISPLAY DEVICES CONT’D…
• Speech synthesizer – a recent development is the ability not only to display text on a
monitor but also to read the text to you. Thus, you could receive a text email from a
colleague and the system could read that email to you. This is of enormous benefit to
the visually impaired when using a computer. On the flip side, it is now possible to use
a microphone to talk to the computer and for the computer to directly convert the
spoken word into text which will be displayed within say your word-processor. Whilst
these systems are far from fool proof they are getting better as more advanced
software is being made available
25. OUTPUT/DISPLAY DEVICES CONT’D…
• Printers – is an output device that produces text and graphics on a physical medium
such as paper or transparency film. Printed information, called hard copy, exists
physically and is more permanent form of output than that presented on a display
device (soft copy).
• A hard copy, also called a printout, is either in portrait or landscape orientation.
Types of printers
• Laser printers
• Colour laser printers
• Inkjet printers
• Dot Matrix printers
26. MAIN PARTS OF THE COMPUTER
• Central Processing Unit (CPU): The Central Processing Unit or
CPU can be thought of as the brain of the computer. The function of
the CPU is to execute the instructions in the programs.
• CPU comprised of three main parts: Arithmetic Logical Unit (ALU),
Control Unit and Registers.
• Speed measurement: The speed of Central Processing Unit (CPU)
is measured by Hertz (Hz).
• ALU: Executes all arithmetic and logical operations. Arithmetic
calculations like as addition, subtraction, multiplication and division.
Logical operation like compare numbers, letters, or special characters
• Control Unit (CU): controls and co-ordinates computer
• Registers :Stores the data that is to be executed next, "very fast
Primary and Secondary Memory.
• Primary memory: RAM and ROM
Random Access Memory (RAM): Volatile (Lose data when the
computer switches off or loose power). When the Computer switches
On, the Operating System (OS) is temporarily loaded on RAM.
Read Only Memory : Non-Volatile(ROM is a permanent form of storage. ROM stays
active regardless of whether power supply to it is turned on or off. ROM devices do not
allow data stored on them to be modified.
• Secondary Memory : Stores data and programs permanently :its retained
after the power is turned off.
30. STORAGE DEVICES
• A storage device is the computer hardware that records and/or retrieves items to and
from storage media. A storage medium is the physical material on which a computer
keeps data, instructions, and information.
• Three common types of storage media are hard disks, flash memory, and optical discs.
• Hard disk- is a storage device that contains one or more inflexible, circular platters
use magnetic particles to store data, instructions, and information. Data and
instructions are store in tracks and sectors of a platter.
32. STORAGE DEVICES….
• Flash Memory- Flash memory is a type of memory that can be erased electronically
• E.g. Memory Card and USB.
• Optical Disk- An optical disc is a flat, round, portable metal disc with a plastic coating.
• E.g. CD, DVD and Blu-ray Disk
• Cloud Storage-is an Internet service that provides hard disk storage to computer users
33. UNIT OF MEASUREMENT
• Bit- All computers work on a binary numbering system, i.e. they
process data in one's or zero's. This 1 or 0 level of storage is called a
• Byte- A byte consists of eight bits.
• Kilobyte-A kilobyte (KB) consists of 1024 bytes.
• Megabyte- A megabyte (MB) consists of 1024 kilobytes.
• Gigabyte- A gigabyte (GB) consists of 1024 megabytes.
34. DATA, INFORMATION AND
• Data- Unstructured facts or figures
• Information –Processed data (For data to become information, it
must be contextualized, categorized, calculated and condensed).
• Knowledge- Knowledge is closely linked to doing and implies know-
how and understanding.
37. WHAT IS SOFTWARE?
• The software is the collection of instructions which makes the computer work. For
instance, when you type words via keyboard, the software is responsible for displaying
the correct letters, in the correct place on the screen. The software is held either on
your computer’s hard disk, CD-ROM, DVD or on a diskette (floppy disk) and is loaded
(i.e. copied) from the disk into the computers RAM (Random Access Memory), as and
• Software is divided commonly into two main categories: (1) System software: controls
the basic (and invisible to the user) functions of a computer and comes usually
preinstalled with the machine. (2) Application software: handles multitudes of common
and specialized tasks a user wants to perform, such as accounting, communicating,
data processing, word processing.
38. WHAT IS AN OPERATING SYSTEM?
• The operating system is a special type of program which loads automatically when you
start your computer. The operating system allows you to use the advanced features of
a modern computer without having to learn all the details of how the hardware works.
Types of Operating Systems
• Microsoft windows
• IBM produced an operating system called OS/2 but this was largely ignored and is only
used by few companies.
• UNIX and Linux are other examples of operating systems which may be run on PCs.
• Other types of computers, such as those manufactured by Apple have a completely
different operating system.
39. FUNCTION OF OPERATING SYSTEM
• Processor management : It manages the assignment of processor to different tasks
being performed by the computer system.
• Memory management : It manages the allocation of main memory and other storage
areas to the system programmes as well as user programmes and data.
• Input / Output management : It manages the co-ordination and assignment of
different Input and Output devices while one or more programmes are executed.
• File management.
• Interpretation of commands and instructions.
• Facilitates easy communication between the computer system and the computer
40. EXAMPLES OF SOFTWARE APPLICATIONS
• An application program is the type of program which you use once the operating
system has been loaded. Examples include word-processing programs (for producing
letters, memos etc.) spreadsheets (for doing accounts and working with numbers),
databases (for organising large amounts of information), games programs and
graphics programs (for producing pictures, advertisements, manuals etc.).
• It is important that you recognise examples of application programs covering the
– Word processing
– Web browsing
– Photo editing
– Computer games
41. SOFTWARE APPLICATIONS CONT’D…
• Word processing application – (such as Microsoft word) allows you to produce
letters memos, etc., easily. You can easily mail merge a list of names and addresses to
produce mass mailers, individually addressed to customers or subscribers.
• Spreadsheets application – (such as Microsoft Excel) allows you to work out a
company’s income, expenditure and then calculate the balance. It enables you to make
‘what if’ projections and to forecast how changes in prices will affect profits.
• Database application – (such as Microsoft Access) allows you to compile information
and then to search this information to extract just the information you require. For
instance, if you have a database of all the equipment housed within an office you can
vey simply produce a report listing the equipment housed within an office you can
very simply produce a report listing only the equipment above a certain value.
42. SOFTWARE APPLICATIONS CONT’D…
• Presentation application – (such as Microsoft PowerPoint) allows you to produce
professional looking presentations, which can be printed out directly onto slides for
use with an overhead projector. Alternatively, you can display your presentations
directly on a computer screen or via a computerised projector.
• E-mailing application – there are many email programs available. As the name
suggests you use these to send and receive emails. Microsoft Outlook is supplied
within Microsoft office. Another well known example is the Thunderbird email
• Web browsing applications – applications used to view and interact with the World
Wide Web (WWW).
– Microsoft Internet Explorer
– Netscape Navigator
– Mozilla Firefox
43. SOFTWARE APPLICATIONS CONT’D…
• Photo editing applications - these programs allow you to edit digital photos. You
can adjust items such as the picture brightness, contact and colour balance. You can
remove defects such as the red eye effect often caused when using a flash. You can
apply interesting special effects and filters to visually enhance your photographs.
Examples include Photoshop from Adobe and Paint Shop Pro from Correl.
• Computer games – started off as simple bat and ball games and today have evolved
into an enormous worldwide business. There are many different types of games
ranging from the educational, to the ‘shoot them up’ variety. The level of graphical
detail on the screen gets better each year.
44. OPERATING SYSTEM VS APPLICATION
• The operating system works closely with the hardware that you have installed within
your computer. It interprets the input entered via the mouse or keyboard and outputs
data to the screen.
• The application programs sit above the operating system, make use of the
functionality built into the operating system. They are specific to a particular task. For
instance Microsoft word is designed as a word processing program, while Microsoft
Excel is a spreadsheet program.
46. WHAT IS A NETWORK
• A network is a collection of computers and devices connected together via
communications devices and transmission media. Many businesses network their
computers together to facilitate communications, share hardware, share data and
47. TYPES OF NETWORKS
• LAN (Local Area Network) – is a network that connects computers and devices in a
limited geographical area such as a home, school computer laboratory, office building,
or closely positioned group of buildings.
• WLAN (Wireless Local Area Network) – is a LAN that uses no physical wires. Computers
and devices that access a wireless LAN must have built-in wireless capability or the
appropriate wireless network card, PC Card or flash card.
48. TYPES OF NETWORKS CONT’D…
• WAN (Wide Area Network) – is a network that covers a large geographic area (such as
a city, country, or the world) using a communications channel that combines many
types of media such as telephone lines, cables and radio waves.
49. TYPES OF NETWORKS CONT’D…
• Client/Server Network – one or more computers act as a server, and the other
computers on the network request services from the server. A server is sometimes
called the host computer, controls access to the hardware, software and other
resources on the network. The clients are other computers and mobile devices on the
network that rely on the server for its resources.
50. THE INTERNET
• The internet is a global collection of networks that connects millions of businesses,
government agencies, educational institutions and individuals. Its access is provided
by ISPs. It runs on www, ftp, html. More than one billion people around the world use
the internet daily for a variety of reasons , including the following:
– Communicate with and meet other people
– Access a wealth of information, news and research findings
– Shop for goods and services
– Bank and invest
– Take a class
– Download music
– Share information
51. WORLD WIDE WEB (WWW)
• The World Wide Web (WWW) is a collection of text documents and other resources,
linked by hyperlinks and URLs. Usually accessed by web browsers. Its an application
running on the internet. The WWW is basically the text and pictures which you can
view using your web browser, such as Microsoft Internet Explorer or Netscape
52. INTRANET & EXTRANET
• An Intranet is a smaller, closed version of the internet, which can only be accessed by
authorised members of an organisation. Intranets are becoming an increasingly
popular way to share information within a company or other organisation. An intranet
uses internet technologies to allow users to access company documents, search
databases, schedule meetings and of course send emails.
• An Extranet is an Intranet which is partially accessible to authorised outsiders. An
extranet allows outsiders who have been issued with a password to gain limited access
to information held on a company network. Extranets are being used as a way for
business partners to share information.