1.Introduction to Computer

I. INTRODUCTION TO COMPUTERS & WINDOWS

I.1 DEFINITION OF COMPUTER

A computer is an electronic device or a tool which accepts data1 or information2 in one form and processes it to produce data or information in another form i.e. in a more meaningful manner. It accepts data as its input, process data according to the predefined rules (programs3) and supplies results(output) in the form of data and/or actions. It can convert data into information that is useful to people. In other words a computer is a machine which collects, stores, retrieves, manipulates and transmits information.

A complete computer system includes four distinct parts:  Hardware  Software  Data  User

Hardware: •A computer's hardware consists of electronic devices; the parts you can see and touch. It consists of its processors, its storages, its input/output devices and its communication connections (i.e. the actual machinery: wires, transistors and circuits. ) •The term "device" refers to any piece of hardware used by the computer, such as a keyboard, monitor, modem, mouse, etc.

1 Data is a collection of basic facts (symbols that represent facts, objects, and ideas) e.g. name, age, salary etc. 2 Information is the data, which is processed into meaningful form 3 A program is a set of instructions which are written in a computer language to perform certain tasks.

Software: •Software – general term used to describe all the various programs – consists of organized sets of instructions for operating the computer system.•Some programs exist for the computer's use, to help it manage its own tasks and devices; These operations may include identifying, accessing and processing information.•Other programs exist for the user, and enable the computer to perform tasks for you, such as creating documents. Data: •Data consists of raw facts, which the computer can manipulate and process into information that is useful to people. •Computerized data is digital, meaning that it has been reduced to digits, or numbers. The computer stores and reads all data as numbers. •Although computers use data in digital form, they convert data into forms that people can understand, such as text, numerals, sounds, and images.

Users: •People are the computer's operators, or users. • Some types of computers can operate without much intervention from people, but personal computers are designed specifically for use by people. I.2 TYPES OF COMPUTERS Computers can be generally classified by size and power as follows, though there is a considerable overlap: Supercomputers •Supercomputers are the most powerful computers. They are used for problems requiring complex calculations. An extremely faster computer that can perform hundreds of millions of instructions per second. •Because of their size and expense, supercomputers are relatively rare.•Supercomputers are used by universities, government agencies, and large businesses.

Mainframe computers •Mainframe computers can support hundreds or thousands of users simultaneously, handling massive amounts of input, output, and storage.•Mainframe computers are used in large organizations where many users need access to shared data and programs.•Mainframes are also used as e-commerce servers, handling transactions over the Internet. In the early days of computing, mainframes were huge computers that could fill an entire room or even a whole floor! As the size of computers has diminished while the power has increased, the term mainframe has fallen out of use in favor of enterprise server.

Minicomputers •Minicomputers are smaller than mainframes but larger than microcomputers. • Minicomputers usually have multiple terminals4. Minicomputers are multiprocessing systems capable of supporting from 4 to about 200 users simultaneously. • Minicomputers may be used as network servers and Internet servers. Minicomputers are normally referred to as mid-range servers now.

Multiprocessing: 1) Refers to a computer system’s ability to support more than one process (program) at the same time. 2) Refers to the utilization of multiple CPUs in a single computer system. This is also called parallel processing.

Workstations •Workstations are powerful single-user computers.•Workstations are used for tasks that require a great deal of number- crunching power, such as product design and computer animation.•Workstations are often used as network and Internet servers. The leading manufacturers of workstations are Sun Microsystems, Hewlett–Packard Company, Silicon Graphics Incorporated and Compaq.

4 A terminal is a device with a monitor and a keyboard. Some terminals have no processing power and must connect to a server to operate. Others have the capability of functioning when not connected to the server. 4

Microcomputers, or Personal Computers •Microcomputers are more commonly known as personal computers (PC). The term "PC" is applied to IBM-PCs or compatible computers. The personal computer (PC) defines a computer designed for general use by a single person. PCs were first known as microcomputers because they were a complete computer but built on a smaller scale than the huge systems in use by most businesses. Full-size desktop computers are the most common type of PC.

•Notebook (laptop) computers are used by people who need the power of a desktop system, but also portability. They integrate the display, keyboard, a pointing device or trackball, processor, memory and hard drive all in a battery-operated package slightly larger than an average hardcover book.

• Handheld PCs (such as PDAs: personal digital assistants also known as Palmtop) lack the power of a desktop or notebook PC, but offer features for users who need limited functions and small size. Palmtops are tightly integrated computers that often use flash memory instead of a hard drive for storage. These computers usually do not have keyboards but rely on touchscreen technology for user input. Palmtops are typically smaller than a paperback novel, very lightweight with a reasonable battery life. A slightly larger and heavier version of the palmtop is the handheld computer.

•Wearable Computers - The latest trend in computing is wearable computers. Essentially, common computer applications (e-mail, database, multimedia, calendar/scheduler) are integrated into watches, cell phones, visors and even clothing!

Examples of Computer Usage

We use computers in our daily lives. At home, PC is used for business (e.g. word processing), personal Information manager, personal finance, online banking, tax preparation, E-mail, instant massaging, and chat rooms, entertainment (e.g. music composition, greeting cards), education ,etc.

At work (small office/Home Office), PC can be used for business, company specific (e.g. accounting, legal reference), network management, web browser, etc.

As a mobile user, you can use a portable computer for business, e-mail etc.

In large Business, they use PCs connected to minicomputers, for business, accounting, network management, web browser, E-mail, etc.

In big industries, computers are used in a wide variety of tasks such as desktop publishing, computer aided design (CAD); with workstations connected to mainframes or minicomputers; etc. I.3 ADVANTAGES/DISADVANTAGES OF COMPUTERS a. Advantages of Using Computers in Information Processing

Some advantages of using computers in information processing include

 Speed: Tasks can be completed faster because computers work at amazing speed. Typically more than 500,000 instructions can be processed each second.  Accuracy: Computers can process large amounts of data and generate error-free results, provided that the data is entered correctly  Storage & Retrieval: Computers can store enormous amounts of data for future use. Data stored in computers is readily available and can be accessed at very high speeds.  Automation: Due to its ability to follow a set of instruction; tasks can be completed with little human intervention (i.e. automatic).  Low cost: Though initial investment may seemingly be high, running and maintenance costs become lower in the long term.  High volumes: Due to speed to execution and storage facilities the computer is ideal for jobs of high volume.  Repetitive Operations: In situations where identical operations have to be performed on sets of data e.g. for Payroll the computer follows the same set of instructions at fast speeds having error free results.  The high reliability of components inside modern computers enables computers to produce consistent results.  Efficiency and productivity can be raised.  Overall security can be raised due to less human intervention.  Customer services can be improved due to more efficiently management and operations.  Computers with communicating capability can share data and information with other computers. b. Disadvantages of using computers for information processing include

 Unemployment: Some jobs may be lost due to computerization and thus lower the morale of staff members.  Face-to-face interactions among staff may be reduced.  It needs trained people: Some staff has to be trained or retrained  Expensive: - Initial investment cost can be high. - Extra cost is required to employ specialized staff to operate and design the data processing system. I.4 BLOCK STRUCTURE OF COMPUTERS & FUNCTION OF COMPONENTS

All general purpose computers require the following hardware components:

OUTPUT

DEVICES

CPU

INPUT DEVICES Figure: Components of a computer 6

A computer's hardware devices are categorized as follows: •Processor •Memory •Input and output (I/O) devices •Storage devices Central Processing Unit (CPU): The heart of the computer, this is the component that actually executes instructions Memory: Enables a computer to store, at least temporarily, data and programs. Input devices: Usually a keyboard and mouse, the input devices is the conduit through which data and instructions enter a computer. Output devices: A display screen, printer, or other device that lets you see what the computer has accomplished Mass storage device: Allows a computer to permanently retain large amounts of data. Common mass storage devices include disk drive and tape drives. 1) The CPU The procedure that transforms raw data into useful information is called processing (i.e. manipulation of data). This function is divided between the computer's processor and memory. The processor is also called the central processing unit (CPU). It manages all devices and performs the actual processing of data. The CPU consists of one or more chips attached to the computer's main circuit board (the motherboard). It is one of the most important element of the personal computer. On large machines, CPUs require one or more printed circuit boards. On personal computers and small workstations, the CPU is contained on a single integrated circuit called the microprocessor. The computer will not run without a CPU.

Keyboard Processor Printer

ALU M E VDU: Visual

M Display Unit Control O

Unit R Y Plotter Scanner Central Disk Drive memory Input Output Devices Devices

Figure: Schematic Diagram of a computer The CPU contains two basic components: 7

A control unit extracts instructions from memory and decodes and executes them, calling on the ALU when necessary.

The Arithmetic/Logic Unit (ALU) performs both arithmetic and logical operations. Arithmetic operations are fundamental math operations like addition, subtraction, multiplication, and division. Logical operations such as the AND, OR, and XOR are used to make comparisons and decisions, and these determine how a program is executed.

System clock: It controls the speed of computer operations, generates regular electronics pulses, or ticks. Each tick is called a clock cycle. A CPU requires a fixed numbers of clock cycles to execute each instruction. Speed at which computer executes instructions is called clock speed or clock rate and is measured in megahertz (Mhz).

2) Memory

The term memory identifies data storage that comes in the form of chips attached to the motherboard, and the term storage is used for memory that exists on tapes or disks. Moreover, the term memory is usually used as shorthand for physical memory, which refers to the actual chips capable of holding data. Some computers also use virtual memory, which expands physical memory onto a hard disk.

Memory holds data and program instructions as the CPU works with them. This memory is called Random Access Memory (RAM) or Main Memory. Every computer comes with a certain amount of physical memory (RAM). You can think of main memory as array of boxes, each of which can hold a single byte of information. The CPU can find any piece of data in RAM, when it needs it for processing.

– How Memory is measured

•The smallest usable unit of measure for memory is the byte – the amount of memory required to hold one character, like the letter A or the numeral 2.•Computers work with larger chunks of data, measured in multiple bytes, as shown below:

Storage Term Approximate Number of Bytes Exact Number of bytes Kilobyte (KB) 1 thousand 210 or 1,024 Megabyte (MB) 1 million 220 or 1,048,576 Gigabyte (GB) 1 billion 230 or 1,073,741,824 Terabyte (TB) 1 trillion 240 or 1,099,511,627,776 Petabyte (PB) 1 quadrillion 250 or 1,125,899,906,842,624 Exabyte (EB) 1 quintillion 260 or 1,152,921,504,606,846,976 (1 byte = 8 bits5)There several different types of memory:  RAM ( pronounced ramm, acronym for Random Access Memory,): This is the same as main memory. When used by itself, the term RAM refers to read and write memory; that is, you can both write data into RAM and read from RAM.

This is in contrast to ROM, which permits you only to read data.

RAM can be accessed randomly; that is, any byte of memory can be accessed without touching the preceding bytes. RAM is the most common type of memory found in computers and other devices, such as printers.

There are two basic types of RAM:  Dynamic RAM (DRAM)  Static RAM (SRAM)

The two types differ in the technology they use to hold data, dynamic RAM being the more common type.

5 Bit is short for Binary Digit. Bits have value of 1 or 0, (or on or off, or, true or false) 8

Dynamic RAM needs to be refreshed thousands of times per second. Static RAM does not need to be refreshed, which makes it faster; but it is also more expensive than dynamic RAM. Both types of RAM are volatile, meaning they hold data only when the power is on. When the power is off, RAM's contents are lost.

 ROM (Read Only Memory): Computers almost contain a small amount (a few thousands of bytes) of ROM that holds instructions for starting up/ booting the computer and perform diagnostics. Unlike RAM, ROM cannot be written to. In fact, both types of memory (ROM and RAM) allow random access. To be precise, therefore, RAM should be referred to as read/write RAM and ROM as read-only RAM.

 PROM (Pronounced prom, an acronym for Programmable Read Only Memory). A PROM is a memory chip on which you can store a program. But once the PROM has been used, you cannot wipe it clean and use it to store something else. Like ROMs, PROMs are non-volatile.

The difference between a PROM and a ROM is that a PROM is manufactured as blank memory, whereas a ROM is programmed during the manufacturing process. To write data onto a PROM chip, you need a special device called PROM programmer or PROM burner. The process of programming a PROM is sometimes called burning the PROM.

 EPROM (Acronym for Erasable Programmable Read Only Memory and pronounced ee-prom). An EPROM is a special type of ROM that can be erased by exposing it to ultraviolet light. The ultraviolet light clears its contents, making it possible to reprogram the memory. To write to and erase an EPROM, you need a special device called a PROM programmer or PROM burner.

An EPROM differs from a PROM in that a PROM can be written to only once and cannot be erased. EPROM’s are used widely in personal computers because they enable the manufacturer to change the contents of the PROM before the computer is actually shipped. His means that bugs can be removed and new versions installed shortly before deliver.

 EEPROM (Acronym for Electrically Erasable Programmable Read Only Memory and pronounced double-eeprom or e-e-prom). An EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge. Like other types of PROM, EEPROM retains its contents even when the power is turned off. Also like other types of RM, EEPROM is not as fast as RAM.

EEPROM is similar to flash memory (sometimes called flash EEPROM). The principal difference is that EEPROM requires data to be written or erased one byte at a time whereas flash memory allows data to be written or erased in blocks. This makes flash memory faster.

 SSD (Solid State Disk) are high performance plug-and-play storage devices that contain no moving parts. SSD components include either DRAM or EEPROM memory boards, a memory bus board, a CPU, and a battery card.

Because they contain their own CPUs to manage data storage, they are a lot faster than conventional rotating hard disks; therefore they produce highest I/O (input/output) rates. SSDs are most effective for server applications and server systems, where I/O response time is crucial.

3) Input and Output (I/O) devices 3.1 Definition of Input Devices and Examples

What is input?

Input is any data or instructions provided to the computer by a person, the environment, or another computer. People have a variety of options available to input data and instructions into a computer. information.

Input data is a collection of unprocessed text, words and symbols; numbers; pictures; audio signals from a microphone; signals from another computer; temperature, speed, pressures and video. Once data is in memory, the computer interprets and executes instructions to process the data into information.

Instructions are the steps that tell the computer how to perform a particular task. Instructions entered into the computer can be in the form of programs, commands and user responses.

A program is a series of instructions that tells the computer what to do and how to do it. When a programmer writes a program, he or she inputs the program into the computer by using a keyboard, mouse or other input device. Programs respond to commands that a user issues.

A command is an instruction that causes a program to perform a specific action.

A user response is an instruction a user issues by replying to a question displayed by a program. A response to the question instructs the program to perform certain actions.

What are input devices?

Input devices accept data and instructions from the user or from another computer system. An input device is any hardware component that allows users to enter data or instructions (programs, commands, and user response) into a computer. Depending on the application and your particular requirements, the input devices selected may vary. Popular input devices include the keyboard, mouse, scanner, microphone and digital camera. Storage devices such as disk drives serve as both input and output devices.

The keyboard

A computer keyboard is an input device that contains alpha-numeric keys you press to enter data into the computer. Desktop computer keyboards typically have from 101 to 105keys. Computer keyboard are similar to electric typewriter keyboard that contain additional keys. The keys on computer keyboards are often classified as follows:  Alphanumeric keys: letters of alphabet and numbers.  Numeric keypad.  Special keys: function keys, modifier keys and Cursor-movement keys

Most keyboards use the QWERTY layout, named for the first six keys in the top row of letters. The QWERTY keyboard was designed 1800s for mechanical typewriters and was actually designed to slow typists down to avoid jamming keys.

Another keyboard design, which has letters positioned for speed typing, is the DVORAK keyboard. It places frequently typed letters in the middle of the typing area. Most of today’s desktop computer keyboards are enhanced keyboards. An enhanced keyboard has twelve function keys6 along the top, two CTRL keys, two ALT keys, and a set of arrow and additional keys between the typing area and the numeric keypad.

6 Function keys are found across the top of most keyboards and are labeled with the letter F followed by a number. They are special keys programmed to issue commands to a computer. The command associated with the function keys depends on the program.

Desktop computers keyboard often attach via a cable to a serial port, a keyboard port, or a USB port on the system unity. Some keyboard; however, do not use wires at all.

A cordless keyboard is a battery-powered device that transmits data using wireless technology, such as radio waves or infrared light waves. Cordless keyboards communicate with a receiver attached to a port on the system unit.

Long periods of standard keyboards use can cause injuries (repetitive strain injury -RSI) of wrists. Ergonomics keyboards attempt to reduce or eliminate this problem with designs that provide users with more natural comfortable hand wrist and arm position. You also can avoid injuries by adopting correct keyboarding practices

Pointing devices

A pointing device is used to position a pointer on the screen. The pointer can have a number of shapes but is most often an arrow. b.1 Mouse A mouse is a pointing device that fits comfortably under the palm of your hand. The mouse is the most widely used pointing device on desktop computers. It is a small handheld device used to control the movement of a graphical pointer on the screen, often called a mouse pointer in this case. The mouse can be used to issue commands, draw, and perform other types of input tasks. The top and sides of a mouse have one to four buttons, which have different functions depending on what program is running; some also have small wheel called scroll wheel for scrolling through long documents. The bottom of mouse is flat and contains a mechanism that detects movement of the mouse.

There are three basic types of mice:  Mechanical mouse: It has a rubber or metal ball on its underside that can roll in all directions. Mechanical sensors within the mouse detect the direction and the distance the ball is rolling and move the screen pointer accordingly. You should place a mechanical mouse on a mouse pad, which is a rectangular rubber of foam pad that provides better traction than the top of a desk.

 Optical mouse: It has no moving mechanical parts inside. Instead, an optical mouse uses device that emit and sense light to detect mouse’s movement. Some uses optical sensors and others laser. You can place an optical mouse that uses optical sensors on nearly all types of surfaces, eliminating the need for mouse pad. An optical mouse that uses a laser usually requires special mouse pad. An optical mouse is more precise than a mechanical mouse and does not require cleaning as does a mechanical mouse, but it is also more expensive.

Optical sensor

 The above types of mice connect to PCs with a cable that attaches to a serial port, mouse port, or USB port on the system unit.  Cordless mice aren’t physically connected at all. They are battery-powered devices that transmit data using wireless technology, such as radio waves or infrared light waves. The wireless technology used for a cordless mouse is very similar to that of cordless keyboard discussed earlier.

Mouse Techniques

Using the mouse involves five techniques: 1. Pointing; Move the mouse to move the on-screen pointer. 2. Clicking; Press and release the left mouse button once.3. Double-clicking; Press and release the left mouse button twice.4. Dragging; Hold down the left mouse button as you move the pointer.5. Right-clicking; Press and release the right mouse button.

Variants of the Mouse

Trackballs: A trackball is like a mouse turned upside-down. The thumb is used to move the exposed ball and fingers to press the buttons.

Many styles of trackball are available.

Trackpads: A trackpad is a touch-sensitive pad that provides the same functionality as a mouse. To use a trackpad, you glide your finger across its surface. Trackpads provide a set of buttons that function like mouse buttons.

Integrated Pointing Devices: An integrated pointing device is a small joystick built into the keyboard. To use an integrated pointing device, you move the joystick. These devices provide a set of buttons that function like mouse buttons

b.2 Light Pen

A light pen is a handheld input device that can detect the presence of light. Some light pens require a specially designed monitor, while others work with standard monitor.

With a pen-based system, you use an electronic pen to write on the screen and choose commands. To select objects on the screen, a user presses the light pen against the surface of the screen and then presses a button on the pen. Using a light pen is more direct and precise than using a mouse.

Pens are common input devices for handheld computers, like ―personal digital assistants (PDAs).‖ Pens are handy for making notes or selecting commands, not for inputting a lot of text.

Health care professionals use light pens because they can slide a protective sleeve over the pen - keeping their fingers free of contaminants. Light pens are also convenient for applications with limited desktop space such as industrial or manufacturing environments. b.3 Touch Screens

Touch-screen systems accept input directly through the monitor. Touch screens use sensors to detect the touch of a finger. They are useful where environmental conditions prohibit the use of a keyboard or mouse. Touch-screen systems are useful for selecting options from menus.

13 b.4 Game Controllers

The two primary types of game controllers are joysticks and game pads. Game pads usually provide controls for each hand. Joysticks are popular for flight simulator and driving games.

Audio-Visual (Multimedia) Input Devices c.1 Microphones and Speech Recognition Voice Input is the process of entering data by speaking into a microphone. Microphones can accept auditory input. The microphone may be a stand-alone peripheral that sits on top of a desk, or is built into the computer or device, or is in headset. Some external microphones have a cable that attaches to a port on the sound card on the computer. A microphone requires a sound card in the PC.A sound card can digitize analog sound signals, and convert digital sound signals to analog form.

Voice recognition also called speech recognition, is the computer’s capability of distinguishing spoken words. Voice recognition programs do not understand speech. They recognize a vocabulary of preprogrammed words. The vocabulary of voice recognition programs can range from 2 words to millions of words. With speech recognition software, you can use your microphone to dictate text, navigate programs, and choose commands.

Analog Sound Signals Digital Audio Output [electrical signals] (ex. 11100011) to computer Analog Signals are Digitized

C.2 Video Input Video input is the process of capturing full motion images into a computer and storing them on a storage medium such as a hard disk.

Some video devices use analog video signals. Computers, by contrast, use digital signals. To input video from these analog devices, the analog signal must be converted to a digital signal. To do this, plug a video camera or other analog video device into a video capture port on the system unit.

One type of adapter card that has a video capture port is a video capture card, which converts an analog video signal into a digital signal that a computer can use.

The new generation of video camera (cam-corder), called a digital video (DV) camera, records video as digital signals instead of analog signals. To transfer recorded images to a hard disk or CD, users connect DV cameras directly to a USB port on the system unit.

Thus, the computer does not need a video capture card; simply connect the video device to the computer and begin transferring images.

PC video cameras

A PC video camera is a type of digital video camera that digitizes full-motion images. Digital cameras enables a user to capture still images, send email messages with video attachment, add live images to instant messages and make video telephone calls. During the video telephone call, both parties see each other as they talk over the Internet. Video images may be compressed to use less memory and storage space

Web cams

A web cam is a video camera that displays its output on a Web Page.

Optical Input Devices

d.1 Bar Code Readers Bar code readers can read bar codes - patterns of printed bars. The reader emits light, which reflects off the bar code and into a detector in the reader. The detector translates the code into numbers. 15

Flatbed bar code readers are commonly found in supermarkets. Courier services often use handheld readers.

Bar code readers commonly track sales in retail stores

d.2 Image Scanners and OCRImage scanners digitize printed images for storage and manipulation in a computer. A scanner shines light onto the image and interprets the reflection. Optical character recognition (OCR) software translates scanned text into editable electronic documents. There was time when the only way to transfer an existing document (source document7) into the computer was to retype it. Now, however, devices such as optical scanners can capture data directly from a source document. An optical scanner, usually called a scanner, is a light-sensing input device that reads printed text and graphics and then translates the results into a form the computer can process.

Types of scanners:

1. Flatbed Scanner: is similar to a copy machine. The scanning mechanism passes under the item to be scanned, which is placed on a glass surface. Scannable items: single sheet documents, bound material, photograph, some models include trays for slides, transparencies, and negatives.

2. Pen or Handheld Scanner: moves a pen over text to be scanned, and then transfer data to computer. It is ideal for mobile users, students and researchers. Scannable item: any printed text.

3. Sheet-fed Scanner: Item to be scanned is pulled into a stationary scanning mechanism. It is smaller than a flatbed scanner and some models designed specifically for photographs are called photo scanner. Scannable items: single sheet documents, photographs, slides (with an adapter) and negatives.

7 Examples of source documents are order forms, photographs, brochures, or any other document that contains data to be processed. 16

4. Drum Scanner: item to be scanned rotates around stationary scanning mechanism. It is very expensive and is used in publishing industry. Scannable items: single sheet documents, photographs, slides and negatives.

3.2 Definition of Output Devices and Examples

What is output?

Output is the result produced by a computer i.e. data that has been processed into a useful form. A computer generates several types of output, depending on the hardware and software being used and requirements of the user. Users view output on a screen, print it, or hear it through speakers or headsets. While working with a computer, a user encounters four basic categories of output: text, graphics, audio and video.

 Text: Examples of text-based documents are memorandums, letters, reports, announcements, press releases, advertisements, newsletters, envelopes, and mailing labels. On the web, users view and print many other types of text-based documents. These include newspapers, magazines, books, famous speeches, and historical lectures.

 Graphics: Documents often include graphics to enhance their visual appeal and convey information. Business letters have logos. Reports include charts. Newsletters use drawings, clip art, and photographs. Users print high-quality photographs taken with digital camera, eliminating the need for film or film developers. Many Web sites use animated graphics, such as blinking icons, scrolling messages, or simulations.

 Audio: Users insert their favorite music CD in a CD or DVD drive and listen to the music while working on the computer. Software programs such as games, encyclopedia, and simulations often have musical accompaniments for entertainment and audio clips, such as narration and speeches, to enhance understanding.

On the web users turn into radio and television stations and listen to audio clips or live broadcasts of interviews, talk shows, sporting events, news, music, and concerts. They also use Internet to have real time-time conversations with friends, coworkers, or family members, just as if they were speaking on the telephone.

 Video: as with audio, software and web sites often include video clips to enhance understanding. Users watch a live or prerecorded news report, view a movie, see a doctor perform a life-saving surgery, enjoy a live performance of their favorite jazz band on the computer.

Attaching a video camera to the computer allows users to watch home movies on the computer. They can also attach a television’s antenna or cable to the computer and watch a television program on the computer screen.

Output devices return processed data back to the user or to another computer system. An output device is any hardware component that displays, prints, or transmits the results of processing. It conveys information to one or more people. Commonly used output devices are: display devices, printers, speakers, headsets and so on.

A. Display devices – Monitor/ Screen/ VDU (video display unit)

A display device, or simply display is an output device that visually conveys text, graphics and video information. Information on a display device, sometimes-called softy copy exists electronically and displays for a temporally period. Display devices consist of a screen and the components that produce the information on the screen. Desktop computers typically use monitor as their display device. A monitor is a plastic or metal that houses a display device.

Monitors are categorized by the technology they use:

 Cathode ray tube (CRT) 8monitorsFlat-panel9 displays also called LCD monitor.And by the way they display colors: 1. Monochrome – One color on a black background 2. Grayscale – Shades of gray on a white or off-white background 3. Color – From 16 to 16 million unique colors

CRT Monitors In CRT monitors, electrons are fired at phosphor dots on the screen. The dots are grouped into pixels, which glow when struck by electrons. In color CRTs, each pixel contains a red, green, and blue dot. These glow at varying intensities to produce color images.

Flat-Panel Monitors Most flat-panel monitors use liquid crystal display (LCD) technology. Passive matrix LCD uses a transistor for each row and column of pixels. Active matrix LCD uses a transistor for each pixel on the screen. Thin-film transistor displays use multiple transistors for each pixel.

Video Controllers The video controller is an interface between the monitor and the CPU. The video controller contains its own on-board processor and memory, called video RAM (VRAM). B. PC Projectors

A PC projector connects to a PC and is used to project images on a large screen. Digital light processing (DLP) projectors use a microchip containing tiny mirrors to produce very sharp, bright images.

C. Printers - types and operation

8 Cathode Ray Tube (CRT) monitor is a desktop monitor that is similar to a standard television.

9 Flat-panel/ Liquid Crystal Display (LCD) is a desktop monitor that does not use CRT technology, takes up less desk space, and consumes less power than CRT monitor.

A printer is an output device that produces text and graphics on physical medium such as paper or transparency film. Printed information, are called hard copy, exists physically and is a more permanent form of output than that presented on display device (soft copy). A hard copy, also called a printout, is either in portrait orientation or landscape orientation.

Portrait orientation

`````````````` Landscape orientation `````````````` `````````````` `````````````````````````````````````` `````````````` `````````````````````````````````````` `````````````` `````````````````````````````````````` A print out in`````````````` portrait orientation is taller`````````````````````````````````````` than it is wide, while a printout in landscape is wider that it is tall. Question: -Which`````````````` printout orientation ````is used more in writing letters, reports, and books? -Which one ````.is used in spreadsheets, slide shows, and graphic orientation?

Categorizing Printers

Printers fall into two categories: Impact printers use a device to strike an inked ribbon, pressing ink from the ribbon onto the paper. Impact printers are characteristically noisy because of this striking activity. Two commonly used types of impact printers are dot-matrix printers and line printers. Non-impact printers use different methods to place ink /another substance on a page. They form characters and graphics on a piece of paper without actually striking the paper. Some spray ink, while others use heat or pressure to create images. These printers are much quieter than the previously discussed impact printers because non-impact printers do not strike the paper. Commonly used non-impact printers are ink-jet printers, laser printers and plotters.

C.1 Impact Printers

C.1.1 Dot-Matrix Printers

A dot-matrix printer is a common type of impact printer that produces printed images. A dot matrix printer's print head contains a cluster of pins. The printer can push the pins out to form patterns in rapid sequence. The pins press an inked ribbon against the paper, the ribbon creates dots that form characters and graphics. The number of characters per second measures the speed of dot-matrix printer. How Do Dot Matrix Printers Work?

C.1.2 Line Printers

A line printer is a high-speed impact printer that prints an entire line at a time. The number of lines per minute it can print measures the speed of a line printer.

C.2 Non - impact Printers

C.2.1 Ink-Jet Printers An ink-jet printer is a type of non-impact printer that forms characters and graphics by spraying tiny droplets of ink onto the paper. Ink-jet printers have become the most popular type of color printer for use in home because of their lower costs and acceptable quality of print in both black-and-white and color on variety of paper types.

How Do Ink Jet Printers Work?

C.2.2 Laser Printer

Laser printers are high-speed, high-quality non-impact printers, which print text and graphics in a very high quality. They use heat and pressure to bond particles of toner to paper. Laser printers are available for color and black-and-white printing. Usually they cost more than ink-jet printers, and they are much faster. When printing a document, laser printers process and store the entire page before they actually print it. For this reason, laser printers are sometimes called page printers.

C.2.3 Plotters

Plotters are sophisticated printers used to produce high quality drawings such as maps and circuit diagrams. These printers are used in specialized fields such as engineering and drafting and usually are very expensive.

Plotters use mechanical, ink jet, or thermal technology to create

large-format images for architectural or engineering uses.

C.2.4 Snapshot Printers

Snapshot printers are specialized, small-format printers that print digital photographs. Snapshot printers are fairly slow, and can be more expensive to operate

C.2.5 Other High-Quality Printers

Print shops and publishers use these printers to create high-quality color images:  Thermal-wax  Dye-sublimation  Fiery  IRIS

D. Speakers and Headsets

An audio output device is a component for a computer that produces, music speech, or other sounds such as beeps. Two commonly used audio output devices are speakers and headsets. Most speakers have volume control and other controls, which allow user to adjust settings.

3.3 Communication devices

Communications devices (such as modems and network interface cards) perform both input and output, allowing computers to share information. MODEM Computer’s digital signal must be converted to analog signals before they are transmitted over standard telephone lines. The communication device10 that performs this conversion is a MODEM.

The word, MODEM, is derived from the combination of the words, modulator, to convert digital signal into analog signal, and demodulator, to convert an analog signal into a digital signal.

Both the sending and receiving ends of a standard telephone line must have a MODEM for data transmission. For example, a MODEM connected to a sending computer converts the computer’s digital signal into analog signals. Then analog signal then can travel over a standard telephone line. At the receiving end, another MODEM converts back the analog signals into digital signals that a receiving computer can process.

10 A communication device: is any type of hardware capable of transmitting data, instructions, and information between a sending device and a receiving device. 22

4. Storage Devices

Storage holds data, instruction, and information for future use. Every computer uses storage to hold software, specifically, system software and application software. To start up, a computer locates an operating system (system software) in storage and loads it into memory. When a user issues a command to start application software, such as word processing, the operating system locates the program in storage and loads it into memory.

In addition, to programs user store variety of data and information on computers such as letters, email messages, homework assignments, addresses of friends, photographs and so on.

A storage medium (media is the plural) also called secondary storage is the physical material on which a computer keeps data, instruction and information. The surface of a floppy disk is a storage medium. Items on a storage medium remain intact even when power is removed from the computer. Thus, a storage medium is nonvolatile. Memory, by contrast, typically consists of one or more chips on the motherboard or some other circuit board in the computer and most memory holds data and instructions temporarily and thus is volatile.

Capacity is the number of bytes (characters) a storage medium can hold. For example, a typical floppy disk can store up to 1.44MB of data (approximately 1.4 million bytes) and a typical hard disk has 80GB (approximately 80 billion bytes) of storage capacity.

For analogy, think of a filing cabinet that holds file folders as a storage medium, and the top of your desk as memory. When you want to work with a file, you remove it from the filing cabinet (storage medium) and place it on your desk (memory). When you are finished with the file, you remove it from your desk (memory) and return it to the filing cabinet (storage medium).

The hardware that writes data to or reads data from a storage medium is called a storage device. A floppy disk drive is a storage device.Storage devices hold data not currently being used by the CPU. The two primary storage technologies are magnetic and optical.

Writing is the process of transferring data, instructions and information from memory to storage medium. Reading is the process of transferring these items from storage medium into memory.

A disk drive is a device that reads data from and writes data to a disk. Most new computers feature a floppy disk drive, a hard disk drive, and an optical disk drive.The most common optical storage devices are CD-ROM and DVD-ROM drives. 23

The primary types of magnetic storage are: Diskettes (floppy disks); Hard disks; High-capacity floppy disks; Disk cartridges and Magnetic tape The primary types of optical storage are: CD-ROM (Compact Disk Read-Only Memory); Digital Video Disk Read-Only Memory (DVD-ROM); CD - Recordable (CD-R); CD-Rewritable (CD-RW) and PhotoCD 4.1. Magnetic Storage Devices - How Magnetic Storage Works

Magnetic disk's medium contains iron particles, which can be polarized - given a magnetic charge - in one of two directions. Each particle's direction represents a 1 (on) or 0 (off), representing each bit of data that the CPU can recognize. A disk drive uses read/write heads containing electromagnets to create magnetic charges on the medium. Floppy Disks (Diskettes)

Diskette drives, also known as floppy disk drives, read and write to diskettes (called floppy disks or floppies). They are portable11, inexpensive storage media Diskettes are used to transfer files between computers, as a means for distributing software, and as a backup medium. Diskettes come in two sizes: 5.25-inch and 3.5-inch. A typical floppy disk can store up to 500 double spaced pages of text, several digital photographs, or a small audio file. Floppy disks are available in different capacities, but the most common store 1.44 MB. They are not as widely used as they were ten years ago because of their low storage capacity.

11 With respect to a storage medium, the term portable means you can remove the medium from one computer and carry it to another computer. 24

Some computers use an external floppy disk drive, in which the drive is a separate device with a cable that plugs into a port on the system unit. These external drives are attached to the computer only when the user needs to access items on a floppy disk.

Hard Disks

A hard disk, also called a hard disk drive, is a storage device that uses multiple platters, stacked on a spindle to store data, instructions and information. Each platter has two read/write heads, one for each side. Hard disks use higher-quality media and a faster rotational speed than diskettes.

The system unit on most desktop computers contains at least one hard disk. The hard disk inside the system unit sometimes is called a fixed disk because it is mounted in a drive bay and usually is not portable. Hard disks store large amounts of data. New PCs feature hard disks with capacities of 10 GB and higher.

Two types of portable hard disks are external hard disks and removable hard disks. . An external hard disk is a separate free-standing hard disk that connects with a cable to a USB port or other port on the system unit.

. A removable hard disk is a hard disk that you insert and remove from a hard disk drive. Removable hard disks combine high capacity with the convenience of diskettes.

Other Magnetic Storage DevicesHigh-capacity floppy disks offer capacities up to 250 MB and the portability of standard floppy disks. Disk cartridges are like small removable hard disks, and can store up to 2 GB. Magnetic tape systems offer very slow data access, but provide large capacities and low cost. Due to long access times, tape drives are used mainly for backups. 4.2. Optical Storage Devices

- How Optical Storage Works An optical disk is a high-capacity storage medium. An optical drive uses reflected light to read data. To store data, the disk's metal surface is covered with tiny dents (pits) and flat spots (lands), which cause light to be reflected differently. When an optical drive shines light into a pit, the light cannot be reflected back. This represents a bit value of 0 (off). A land reflects light back to its source, representing a bit value of 1 (on). CD-ROMIn PCs, the most commonly used optical storage technology is called Compact Disk Read-Only Memory (CD-ROM).

A standard CD-ROM disk can store up to 650 MB of data, or about 70 minutes of audio. Once data is written to a standard CD-ROM disk, the data cannot be altered or overwritten.

CD-ROM is typically used to store software programs. CDs can store audio and video data, as well as text and program instructions. DVD-ROM

A variation of CD-ROM is called Digital Video Disk Read-Only Memory (DVD-ROM), and is being used in place of CD-ROM in many newer PCs. Standard DVD disks store up to 9.4 GB of data—enough to store an entire movie. Dual-layer DVD disks can store up to 17 GB. DVD disks can store so much data because both sides of the disk are used, along with sophisticated data compression technologies.

Other Optical Storage Devices

1. A CD-Recordable (CD-R) drive lets you record your own CDs, but data cannot be overwritten once it is recorded to the disk. 2. A CD-Rewritable (CD-RW) drive lets you record a CD, then write new data over the already recorded data. 3. Photo CD technology is used to store digital photographs. I.5. SOFTWARE TYPES

Software is a set of electronic instructions that tells the computer how to do certain tasks. A set of instructions is often called a program. When a computer is using a particular program, it is said to be running or executing the program.The two most common types of programs are system software and application software.

I.5.1 System Software

System software exists primarily for the computer itself, to help the computer perform specific functions. System software consists of the programs that control or maintain the operations of the computer and its devices. System software serves as the interface between the user, the application software, and the computer’s hardware.

Two types of system software are operating systems and utility programs. - All computers require an operating system. The OS tells the computer how to interact with the user and its own devices. Common operating systems include Windows, the Macintosh OS, OS/2, and UNIX .

- Several types of utility programs are provided with an operating system. Other utility programs are available as programs separate from the operating system.

1. Operating systems

An operating system (OS) is a set of programs containing instructions that coordinate all the activities among computer hardware resources.

Most operating systems perform similar functions that include starting a computer, providing a user interface, managing programs, managing memory, scheduling jobs, configuring devices, establishing an internet connection, monitoring performance, and providing file management and other utilities.

In most cases, the operating system is installed and resides on the computer’s hard disk. On smaller handheld computers, however, the operating system may reside on a ROM chip.

Different sizes of computers typically use different OS. For example, a mainframe computer does not use the same OS as a personal computer. Even the same types of computers, such as desktop computers, may not use the same OS. Furthermore, the application software for these various OS often is not compatible with each other. For example, PCs use Windows XP, and iMacs use Mac OS X. when purchasing application software, you must ensure that it works with the OS installed on your computer.

The OS that a computer uses sometimes is called the platform. On purchased application software, the package identifies the required platform (operating systems). A cross-platform program is one that has multiple versions, and each version runs identically on multiple OS.

Types of Operating Systems

Many of the first OS were device dependent12 and proprietary13. Some operating systems still are device dependent. The trend today, however, is toward device-independent operating systems that run on computers provided by a variety of manufacturers. The advantage of device-independent operating systems is you can retain existing application software and data files even if you change computer models or vendors.

A. Stand-Alone Operating Systems

A stand-alone operating system is a complete operating system that works on a desktop computer. Some stand-alone OS are called client operating systems because they also work in conjunction with a network operating system. Client operating systems can operate with or without a network. Other stand-alone operating systems include networking capabilities, allowing users to set up a small network.

Examples of stand-alone operating systems are DOS, Windows XP, Mac OS X, OS/2 Warp Client, UNIX and Linux.

 DOS DOS (Disk Operating System) dominated the operating system market during the 1980s. DOS is a single-user OS that supports only 640 KB of memory. DOS features a command-line interface which means it is user-unfriendly, and does not support multitasking or multiprocessing. Later versions included both command-line and menu-driven user interface. Because DOS provides no interface restrictions, DOS applications can look and function differently.

 Windows 3.X Windows 3.0, 3.1, and 3.11 are called the Windows 3.x family. Windows 3.x is an operating environment because it ran on top of DOS, which was the actual OS.

Windows 3.x brought a GUI (Graphical User Interface) and multitasking capabilities to PCs running DOS.

 Windows 95 and 98 o Windows 95 was Microsoft's first true GUI-based, 32-bit OS for Intel PCs. o Windows 95 supports multitasking and can run older DOS and Windows 3.x programs. o Windows 98's features include advanced Internet capabilities, an improved user interface, and enhanced file system performance, among others.  Windows NT o Microsoft's Windows NT was meant as a replacement for DOS, but was too resource-intensive to work on most PCs at the time of its release.Microsoft issued two versions of Windows NT: Windows NT Workstation and Windows NT Server. o NT is a very powerful and robust OS, resistant to system crashes.

 Windows 2000 o Windows 2000 features the same interface and features of Windows 98, with the file system, networking, power, and stability of Windows NT. o Several versions of Windows 2000 are available, each targeting a specific user or computing environment, from home PCs to large enterprise networks.

 Windows XP Since 1990, Microsoft has continually updated its windows operating system, incorporating new features and function with each subsequent version. Windows XP is Microsoft’s fastest, most reliable windows operating system yet, providing quicker startup, better performance, and a new, simplified visual look.  Mac OS X

12 A device dependent program is one that runs only on a specific type or make of computer. 13 Proprietary software is privately owned and limited to a specific vendor or computer model. 28

The Macintosh OS released in 1984; supports the graphical nature of the Macintosh computer. The Mac OS brought the first truly graphical user interface to consumers. The Mac OS also brought interface conformity to the desktop. All applications running under the Mac OS, therefore, provided the same "look and feel" to the user.

The latest version, Mac OS X, is a multitasking operating system available only for computers manufactured by Apple.

 UNIX UNIX: oldest operating system used on PCs; developed in the early 1970s at Bell Labs. UNIX was the first multi-user, multiprocessor, multitasking operating system available for use on PCs. Most versions of UNIX use a command-line interface but some versions offer a GUI.

 OS/2 wrap o OS/2 Warp was the first true GUI-based operating system for Intel-based PCs. o OS/2 is a multitasking OS that provides support for networking and multiple users. It was the first PC OS to feature built-in speech recognition capabilities.

 Linux Linux is a recently developed version of UNIX, which is available for free or at a very low cost from various sources. Linux is a very powerful 32-bit OS that supports multitasking, multiple users, networking, and virtually any application. Linux can run on nearly any type of computer. Linux includes many free programming languages and utility programs. Because of its power and openness, Linux is attracting many users, including students, teachers, Internet service providers, and others.

Note: The user interface describes how a user and computer interact with each other. This interaction is typically achieved via hardware devices such as the keyboard, the monitor and (if present) the mouse. - Considering different user interfaces in use today; on the one hand there is the traditional command line style interface (often derided as user-unfriendly interface). Some older operating systems, such as DOS and UNIX, use command-line interfaces. In a command-line interface, you type commands at a prompt. Under command-line interfaces, individual applications do not need to look or function the same way, so different programs can look very different.

- On the other hand, there is the more recent user-friendly interface (often known as a graphical user interface -GUI). Most modern operating systems, like Windows and the Macintosh OS, provide a GUI. A GUI lets you control the system by using a mouse to click graphical objects on screen. A GUI is based on the desktop metaphor. Graphical objects appear on a background (the desktop), representing resources you can use.

B. Network Operating System (NOS)

A NOS typically resides on a server. A NOS is an OS that is designed specifically to support a network. The client computers on the network rely on the server(s) for resources.

Many of the client OS discussed in the previous section work in conjunction with a NOS. Some of the stand-alone OS discussed in the previous section include networking capability. The difference between those and the NOSs discussed in this section is these are designed specifically to support all sizes of networks, including medium to large-sized businesses and web servers.

Examples of NOSs include NetWare, Windows server 2003, OS/2 Warp Server for e-business, UNIX, Linux and Solaris.

2. Utilities

A utility is a program that performs a task that is not typically handled by the operating system. Although operating systems typically include some built-in utilities, many stand-alone utility programs are available for purchase.Some utilities enhance the operating system's functionality. Major categories of utilities include: File defragmentation, Data compression, Backup, Antivirus and Screen saversAntivirus program

The term, computer virus, describes a potentially damaging computer program that affects a computer negatively by altering the way the computer works without the user’s knowledge or permission. More specifically a computer virus is a segment of program code from some outside source that implants itself in a computer. Once the virus is in a computer, it can spread throughout and may damage your files and operating system. Currently more than 61,000 known virus programs exist with an estimated 6 new virus program discovered each day.

Computer programmer of virus, known as virus author intentionally writes a virus program. Some virus author find writing viruses a challenge. Others write them to cause destruction.

To protect the computer against virus attacks, install an Antivirus program and update it frequently. An Antivirus program protects a computer against viruses by identifying and removing any computer viruses found in memory, on storage media, or in files. The two most popular antivirus programs are Mc Afee virus scan and Norton Antivirus. b. File compression

A file compression utility reduces the size of a file(s). A compressed file takes up less storage space than original file. Attaching a compressed file to an email message, for example, reduces the time needed for file transmission. A compressed file sometimes is called a zipped file, when you receive a compressed file you must uncompress it, or unzip, a file, you restore it to its original size.

I.5.2 Development Software/ Programming languages

Development softwares are programming languages used to develop/write application softwares and Operating systems. Examples of commonly used programming languages are Visual Basic, C, C++, Perl, and Java, just to name a few. Programming language is a set of words, symbols and codes that enables a programmer to communicate instruction to a computer. Just as human speaks a variety of languages (English, fresh, Spanish, Kinyarwanda, and so on), programmer use a variety of languages and tools to writ, or cod, a program.

I.5.3 Application Software types & Use

Application software tells the computer how to accomplish tasks the user requires, such as creating a document or editing a graphic image. Applications software consists of programs that perform specific tasks for users.

Application software can be: o packaged software :copyrighted software that meets the needs of a variety of users(MS Office), o custom software : tailor-made software developed at a user’s request(most Management Information Systems - MIS), o freeware : copyrighted software provided at no cost, o public-domain software :software donated for public use with no copyright restrictions o Shareware copyrighted software distributed free for a trial period. o Open source software – makes the source code available to programmers.

Applications software are used for a variety of reasons: 1. As business tools; 30

2. To assist with graphics and multimedia objects 3. To support home, personal, and educational activities 4. To facilitate communications.

Some important kinds of application software are:

Word processing programs Spreadsheet software Database management Presentation programs Graphics programs Networking software Web design tools and browsers Internet applications Communications programs Multimedia authoring Entertainment and education

Categories of application software 1. Business software: Business software is application software that assists people in becoming more effective and efficient in their daily business. Ex: Word processing(Microsoft Word), Spreadsheet(Microsoft Excel), and so on. 2. Graphics and multimedia: Power users such as engineers, architects, desktop publishers, and graphics artists. use sophisticated software that allow them to work with graphics and multimedia. Ex: Video and audio editing, WebPages and so on. Video editing is nothing but modify a segment of video, called a clip, reorders a series of clip or add special effects. 3. Home, personal, and educational software: education software is a software that teaches a particular skill Ex: Paint/ Image editing (for personal use), Clip Art/ Image Gallery and so on 4. Communication software: One of the main reasons people use computers is to communicate and share information with others. Some communication software is considered system software because it works with hardware and transmission media. Other communication software performs specific tasks for users, and thus, is considered application software. and audio editing Ex: Web browser, Instant Messaging, e-mail and so on.

GENERAL PRECAUTIONS User Security All users who use networked computers and share information need to go through security checks before they can be allowed to use the facilities offered by the network. All users have to be first registered in to the computerized system as valid users of the system. Each user is allocated a user name to work with. This is the name used to identify her/himself to the computer system. Each user also chooses a password for herself/himself so that only s/he can use the computer using the name that been allocated to her/him Depending upon the position of the user in the organization s/he can only do operations on the computer which s/he is allowed to do.

The password that the user chooses must be kept a secret. If the password that a user A has is known to user B (say), then it must be immediately changed, otherwise user B can access all private information using A 's password. User B can also do thing which s/he won't be allowed to do using her/his password.

Backups

Another aspect of security is safe guarding data stored on the computer against computer malfunction or device failure. To protect data against computer malfunction or device failure, it is important to take regular backups of data on media which is external to the computers.

Backup means creating or making a duplicate version of any file that you can’t afford to lose. In the event that something does go wrong with the computer and data is no longer accessible another computer should be made available and data restored from the last backups that have been made. 31

Another reason of taking backups is to keep historical data away from the computers main storage as among of space available on the main storage is limited. Whenever access is required to the historical data, it can be restored and accessed provide there is enough space available on the main store.

Power Failure:

External Power Devices: UPS (Uninterruptible Power Supply). An UPS is a power backup system UPS is used when there is a power failure or power interruptions. A UPS is capable of providing power for a range of duration mainly depending on the size of the UPS i.e. the bigger the UPS the greater the time limit provided. An UPS has a battery fitted inside, which provides the power when there is no electricity. The battery is charged when the computer is switched on. The UPS battery should be replaced after may be 2, 4, 5, or 7 years depending of the usage of the UPS and the specifications of the battery. As the time duration of the UPS to provide power eventually reduces. It is an indication that the battery is worn out and thus it should replace it with a new one.

Hardware Failure: depends on the component that fails, a hard disk failure can be a disaster because you might loose all data stored on the hard disk. The effect of hard disk drive failure is considerably reduced if you have completed up to date backup copies of the programs and data files.

Operator error: this refers to a mistake made by a computer user.

Software failure (Computer viruses): Long time ago, two brothers in Pakistan developed accounting software. To prevent from copying their software, the brothers decided to create a computer program which will not let people run the accounting software, if they copied it from somebody.

Computer viruses are programs written by people to create disastrous effects like deleting important information, corrupting software and data, displaying funny things on the screen, while users are working. Sometimes, viruses destroy the system software rendering the computer useless.

Some viruses don't cause any bad effect throughout the year, but on one particular day of the year they destroy everything.

Virus symptoms: -your computer displays vulgar, embarrassing or annoying messages -develops unusual visual or sound effect -seems to work very slow -difficulty in saving files or files mysteriously disappear.

There are three methods of getting rid of viruses 1. To detect and remove viruses many people have developed anti virus software which is able to detect most of the known viruses around. Anti-virus software examines the files stored on a disk to determine whether they are infected with a virus, then disinfects the disk.

2. The sure way of getting rid of viruses is by formatting your disks and re-installing all software and restoring your data, which is virus free.

The processing of formatting a disk destroys all contents of the disk, thereby getting rid of the virus.

3. Finally the best of getting rid of viruses is by not allowing a virus to get into the computer in the first place. This is done by protecting your computer from catching a virus. It is very simple don't copy software from unauthorized sources. Viruses normally come with programs copied from unauthorized sources.

Routine care and Maintenance (Handling)

Computers have to be kept in dust free environments. A normal office air conditioning system maintains rooms dust free. User should avoid eating food, or having drinks, or smoking near computers, as all of these leave behind tiny particles which are dangerous to the proper functioning of computers, Storage devices, like disks, etc. are affected most by these tiny particles. They should always be stored away from dust and covered in boxes.

Conclusion

Computer which is a sophisticated machine is used in many fields in our life. With its accuracy and high speed in processing data, the computer has taken a first place in different area like in medicine, detective agency, information exchange (sending and receiving news and information), education, at home, travel agencies, scientific research, industries, weather forecasting, government, military services, treasury office, etc.

II .Using the Computer and Managing Files

Windows

Windows is now easier to use, more reliable, and more entertaining than ever. Windows and programs open faster than ever before.

Getting started with Windows

Start button is located at the bottom of your program screen when you start Windows for the first time. By default, they are always visible when windows is running. When you click on the start menu ,you see a menu that contains everything you need to begin using windows. You will see shut down, run, help, find,….

Desktop: is the colored area on the screen, because it is just like the surface of a desk, The pictures , too stand for items you might have in your office, here are My computer, My documents, a Recycle Bin…. Icons: pictures that represent the parts of the computer you work with like printer files, folders, programs; simply My computer is also an icon

Starting and Quitting a program.

You can use start button to start any program you want to use, such as MS-Word, Excel,… To start a program 1. Click the start button, and then point to Programs. The program menu appears. 2. Point to the group (such as accessories) that contains the programs you want to start and then click the program name.

To quit a program  Click the close button in the upper-right corner of the program window.

Opening a Document, File or Folder There are several ways to open a document in Windows. -You can use the document command on the start button (Start  document) -You can open a document from within the program On the File menu, click Open (File  Open) -After you have located the file you want, you can double-click to open it. To open a file or folder 1. On the desktop, double-click My computer. The My computer window opens. 2. Double-click the drive that contains file or folder you want to open. 3. Double-click the file or folder

Renaming Files and Folders

If you decide to change the name of File or Folder, you can quickly rename it. To renaming file and folder - In a window, select a file or folder you want to rename. - On the file menu, click Rename. - Type a name and then press Enter.

Getting Help

Windows Help is your principal source of information about any version of Windows . This is essential to learning and using windows. The are 2 types of help: - help about a specific procedure (help in program such as Word pad, MS-word,…) - help which gives you information about what you see on your screen To open windows Help  Click the Start button, and then click Help. The windows Help window appears. 35

Each tab helps you locate information in a different way. Use the content tab to locate topics, the Index tab to look up keywords, and the search tab to search for text.

Finding something on your computer (Files and Folders)

When you are looking for a particular folder or file, you can use the Find (or Search) command instead of opening numerous folders. The Find command lets you quickly search a specific drive or you entire computer.

To find a file or folder

1. Click the Start button, point to Find (or Search), and then click Files or Folders. The Find dialog box appears. 2. In Named, type the file or folder name you want to find. 3. Click the look in down arrow, or click Browse to specify where to search. 4. Click Find Now (or Search).

Understanding Files

Definition File is a collection of related records Folder is a collection of related files

Most of the data you use on your computer is organized into files. You create the files using your application programs. For example every word processing document is a file, every spreadsheet is also a file, and so on.

An entire file name is made up of two parts: the file name and an extension. The file name and extension are separated by a period. e.g: MYLETTER.DOC: a file name MYLETTER with extension DOC MYLETTER: TXT: a file name MYLETTER with extension TXT. DATA.WK1: a file name DATA with extension WK1.

Folder names do not usually include extensions.

REPORT.DOC is a valid file name. REPORT is the file name, and DOC is the extension. The file name should tell you what the report contains; the extension often tells you the type of file. Some application programs assign an extension automatically. For example in MS-WORD usually files are kept with extension DOC. REP ORT DOC is not valid file name because a file name cannot include spaces. You should give to a file and a folder, names .

Note: -Name should clearly identify or reflect the contents of the item. -Within one folder, subfolder and files must have unique names. However, you can have another subfolder or file with the same if it is stored in another folder. For example you can have a file named STUDREC.DOC stored in both the STUDENTS subfolder as well as in KIST folder on drive C, but you cannot have two files named STUDREC.DOC in the same folder.

Using Wild Card.

When you want to work with a group of files, you can type wild cards within file names. There are two wild cards: the asterisk {*} and the question mark {?} The question mark wild card {?} is used in place of any single character. The asterisk wild card {*} is used in place of a single character and all the characters that follow it

You can use wild cards in different combinations to control which files are included in a group. Suppose that you are writing a book that has nine chapters. The file for each chapter is named CHAP, followed by the chapter number, a period, and the file extension DOC. When you want to copy all the files {chap. DOC through CHAP.DOC}, you can use : CHAP? DOC This file uses the? wild card and includes every file name beginning with CHAP and followed by any single character and DOC extension. Remember that each ? Wild card represents only one character.

Suppose that your book contains 20 chapters and files are named CHAP1.DOC through CHAP20.DOC. You need to use a different wild card the asterisk. To copy all the files for this book, you can use CHAP* .DOC This file includes every file name beginning with CHAP, followed by any number of characters and the DOC extension. Remember that the * wild card represent any number of characters.

Starting a program by using the run command

You can use Run command to start programs, open folders, and connect to network resources. The Run command is located on the Start menu.

To use the Run command

1. Click the Start button, and then click Run. 2. Type the path or the program name, and then click OK. 37

If you are not sure where the program is or how to specify the path, click the browse button.

Shutting down your computer

Do not turn off your computer until you see a message telling you that shutdown is complete. If you turn off your computer without shutting it down correctly, you risk losing information or damaging your files.

To shut down your computer

1. Click the Start button, and then click Shut Down. The Shut Down Windows dialog box appears.

2. Click OK if you want to turn off your computer. If your computer doesn’t turn off automatically, a message appears when you can safely turn off your computer.

Creating Folders

A folder contain files. To keep your things organized ,your work is stored in folders.

To create folders

1. On the desktop, double-click My Computer The My Computer window opens. 2. Double-click the disk drive or folder in which you want to create a folder The drive or folder window opens. 3. On the File menu, point to New, and then click Folder.

4. Type a folder name, and then press Enter. The new folder appears in the location you selected.

Seeing what’s on your computer

In Windows, the things you have on your computer i.e your programs, documents and data files all are accessible from one place called ‘My Computer’. When you first start Windows, my computer appears on the screen(desktop).When you click my computer, a window appears displaying several different pictures called icons. To use an item in my computer, double click the icon.

Another way of seeing what’s on your computer is to use Windows Explorer .Opening Windows Explorer gives you a view of your computer’s contents as a hierarchy or tree. You can easily see the contents of each drive and folder on your computer (Start  Program  Windows Explorer) Organizing files and folders

In windows you can organize your documents and programs to suit your preferences. You can store these files in folders, and you can move, copy, rename and even search for files and folders.

Working within documents

Copying and Moving Files and Folders

To copy or move a file or folder

1. In a window, select a file or folder you want copy or move. 2. On the Edit menu, click Copy, to copy the file, or click Cut to move the file. 3. Double-click the folder in which you want to place the file or folder . 4. On the Edit menu, click Paste. The file appears in its new location.

Using windows efficiently

Windows provides some special features to speed up the way you work.In addition to the button on the right mouse to access and move information faster or to create shortcuts to documents, programs and other items. 39

You can quickly copy file to a floppy diskette by double clicking ‘send to ‘ after you use your rigth mouse button to click the file icon.

Putting shortcuts on the desktop provide easy access to the documents and programs you often use.You can then open the document without having to find it first, by double-clicking the shortcut icon. A shortcut does not change the file’s location, it just lets you open the file quickly.

You can create a shortcut to any object including folders,disk drives,other computers or printers.

To put shortcut on the desktop:

1. In My computer,or Windows Explorer ,locate the item you want easy access to 2. Use the right mouse to drag the item to desktop 3. Click create shortcut here. Finally,the shortcut appears on your desktop.