Introduction to computer_hardware
- 1. RESTRICTED RESTRICTED 1 INTRODUCTION TO COMPUTER HARDWARE CHAPTER ONE INTRODUCTION DEFINITION OF COMPUTER. 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, process the data according to specified rules, produce results, and stores the results for future use. In other words, a computer can generally be defined as an electronic device that does computation and makes logical decisions according to instructions and data that have been given to it. Thus the phrase “garbage-in-garbage-out.” Data and Information Computers process data into information. Data can be defined as a collection of unprocessed items or files, which can take the form of; text, numbers, images, audio, and video. Information can also be defined as processed or refined data items which conveys meaning and is useful to people. Many daily activities either involve the use of or depend on information from a computer. Information Processing Cycle Computers process data (input) into information (output). Computers carry out processes using instructions, which are the steps that tell the computer how to perform a particular task. A collection of related instructions organized for a common purpose is referred to as Software. A computer often holds data, information, and instructions in storage for future use. Some people refer to the series of input, process, output, and storage activities as the Information Processing Cycle. Most computers today communicate with other computers. As a result, communications also has become an essential element of the information processing cycle. PROCESSINPUT OUTPUT STORAGE
- 2. RESTRICTED RESTRICTED 2 CHARACTERISTICS OF COMPUTER. SPEED: The computer can process information many thousand times faster than the human brain. What could take a man some hours to accomplish may take a computer a few seconds. ACCURACY: The probability of error from a slim, in most cases, errors output are a result of input by the computer or programmer. Thus the saying “garbage in garbage out” DURABILITY: The computer lasts more than lifetime. Computers designed and built in the 80s are still functioning today. AUTOMATIC: Human supervision is usually required for a lot of work process. The computer does not require human supervision to function. VERSATILITY: The use of computer is no longer limited to educationists and military operations. Every imaginable profession and business now uses it. LIMITATIONS: The Computer has some very serious limitations. It is incapable of thought, lacks initiative and cannot react to unforeseen (unprogrammed) events. With the right criteria. It will carry out a deadly function accurately. Where it should produce incremental results and input data has error, the subsequent incremental output will be hugely erroneous and may have fatal consequence. COMPUTER CLASSIFICATION. Classification Based on SIZE: a. Main-frame or Super computer: This is the biggest in both size and capacity. It supports many users at a time, committed via a terminal monitor and keyboard. It is very expensive and consumes electric power. b. Mini-computer: This is bigger than the micro –computer and it supports more than one user. It’s a bit expensive and used mostly in computers. c. Micro-computer: This computer is the smallest in size it has a very high speed and consumes less electric power, it’s made up of micro-chips and it is a less expensive micro-computer support single use e.g. (PC or Desktop computer).
- 3. RESTRICTED RESTRICTED 3 Classification Based On GENERATION: The classification is based on the evolution of electrical or electronic computers. These would further classify digital computers into. a. First Generation Computers: They are made of electrical switches, vacuum tubes and valves. These components were bulky and tended to make the computers large and heavy. The components generated lots of heat and therefore required special cooling systems. b. Second Generation Computers: They are made from electronic switches called transistors. Transistors are semi-conductor devices that generate less heat, lasted longer and are much smaller and lighter. c. Third Generation Computers: They are made of integrated circuit (IC). IC’s are compact transistors placed on a tiny slice of silicon water. This device gave better performance to the computer and greatly reduced the size of the computer. d. Fourth Generation Computers: These are made from greatly enhanced integrated circuits. They are the ones in use today. e. Fifth Generation Computers: These are the computers of the future. They will have artificial intelligence (AI). Classification Based on TYPES: a. Analogue Computer: It is a computer, which operates on continuous data (data obtained by measurement), usually of a physical quantities such as electrical potential, fluid pressures or mechanical motion. Analogue computer is usually a special purpose computer dedicated to a single task. b. Digital Computer: Is a computer, which operates on discrete data (obtained by counting), by manipulating combinations of binary digitsit can perform mathematical calculations, organise and analyse data, control industrial and other processes and simulate dynamic system. c. Hybrid computer: This is a computer that combines the feature of both Analogue and digital computer and is referred to as Anatel. EVOLUTION OF COMPUTER. The historical development of the computer can be associated with human activities such as calculating, counting and so on. All efforts, which are made
- 4. RESTRICTED RESTRICTED 4 to simplify the method of calculation in the past, could be interpreted as attempts at computing. For instance in simple arithmetic, the use of Four Figure Table and Slide Rule are different ways of making calculation easy. It is the quest for way of making improving the method of calculation that led to the invention of Abacus, which is the first machine of that sort. The name Abacus is derived from the Greek word abax, which means, “board” or “calculating table”. The Abacus was probably invented by ancient Sumerians in Mesopotamia before the Hindu-Arabic numeration system became popular. The Abacus was used for counting, adding and subtracting. In a way, it was a mechanical system for counting, consisting of strings and moving beads. This remained the fastest calculating device until 1642 when a French Scientist Blaise Pascal invented another calculating device which use of wheel and cogs. The history of computer can be traced back to the 19th century. When an English inventor Charles Babbage in 1830 developed plans for analytical engine capable of performing arithmetical operations on the basis of instructions from punch card. The analytical engine has – a memory unit to which numbers can be stored: - A Control Unit. - An Input Unit. - An Output Unit and most of other basis element of the present day-computer. Then later in the 20th century, the modern computers came into the development, and their generations are characterised by their technology: a. The First generation computers are the first electronic computers and were developed by the use of “vacuum Tube” as switches, which are used to represent as well control the routing of data (binary digits). Although the tubes worked, they had many problems, as high power consumption and heat generation. They were developed mostly in US after World War II. b. The second generation was introduced somewhere in 1960, used transistor which make them faster, more efficient and consume less
- 5. RESTRICTED RESTRICTED 5 power. The second-generation computers were the first successful commercial computers. c. The third generation computers came in the late 1960s and 1970 were characterised by miniaturisation of components and use integrated circuits (I.C) and Very Large Scale Integrated Circuits (VLSIC), which contain millions of integrated transistors. d. The fourth generation Computers are defined by the introduction of the microprocessor in 1974. The first personal computer falls into this category named IBM 5100. e. The fifth generation computers emphasize on the intensive software development, where Artificial Intelligence is put into use focusing on machine reasoning and logic programming languages. This is yet to be operational. USES OF COMPUTER. The uses of computer can never be over emphasised simple because they are now used in every part of human endeavour. Some of these aspects are: a. As an Office Assistance: This includes the use of computer in word- processing, spread sheet and other utilities. b. In Communications: This includes mobile telephone networks, communicating with satellite c. In Entertainment: This includes graphics in movie making, computerised Audio/visual gadgets and media presentation. d. In Education: This includes, helping students in solving complex problems, easy reference and sources of information. e. In Game Playing: This includes Videogames, Chess Playing. f. In Business: Through Internet and Networks, e-commence and e- Business are in operation, baking online, Shopping on-the net. g. In Remote Sensing: This Includes survey and weather forecasting etc.
- 6. RESTRICTED RESTRICTED 6 APPLICATION OF COMPUTER. IN MILITARY. In military researches: These involve both the research on the development of complex systems, networks, weapons and others for the successful running of the military: a. In weapon control and launching b. In controlling unman planes. c. In navigation and locating of positions by the use of GPS fire control system. IN MEDICINE. Computer is used in the medical centre for: a. Patient diagnosis: This is achieved by the help of medical expert systems b. For analysing the result of test such as ECG scanning in the medical laboratory. c. For keeping patients database: for record retrieving purposes. d. As operation aids. e. In drug monitoring and inventory keeping. IN INDUSTRY. Computer is used in the industries for the following: a. In control rooms: For monitoring of production machineries and their control. b. Computer integrated manufacturing: Data-driven automation that affects all system within a manufacturing environment design and development, production, marketing and sales, and support and service. c. Basic manufacturing functions as well as materials: Handling and inventory control can also be simulated by computer (CIM) before the system is built in an attempt to eliminate wastage. d. In production forecasting: By the use of linear programming production can be forecast and optimise. e. Robots are use in situations that are dangerous to human beings.
- 7. RESTRICTED RESTRICTED 7 CHAPTER TWO BASIC COMPONENTS OF A COMPUTER SYSTEM THE COMPONENTS OF A COMPUTER A computer contains many electric, electronic and mechanical components known as hardware. These components include input devices, output devices, a system unit, storage devices, and communications devices. And also the invisible parts that control the workability of the computer system. The computer system is classified basically into two major parts: Hardware Software HARDWARE Hardware is the physical components of the computer system which you can touch. They are interconnected with cables of various shapes and sizes to facilitate data flow. An example of a piece of hardware is the system unit i.e. the box which houses the central processing unit (CPU) others are printer, scanner, speaker, mouse, keyboard etc. The Primary Components of Computer Hardware Input devices. Output devices. Central Processing Unit (containing the control unit and the arithmetic/logic unit). Storage devices. Memory. Communication devices. INPUT DEVICES An input device is any hardware component that allows you to enter data and instructions into a computer. Five widely used input devices are the keyboard, mouse, microphone, scanner, and Web cam. A computer keyboard contains keys you press to enter data into the computer. For security purposes, some keyboards include a fingerprint reader, which allows you to work with the computer only if your fingerprint is recognized.
- 8. RESTRICTED RESTRICTED 8 A mouse is a small handheld device. With the mouse, you control movement of a small symbol on the screen, called the pointer, and you make selections from the screen. A microphone allows you to speak into the computer. A scanner converts printed material (such as text and pictures) into a form the computer can use. A Web cam is a digital video camera that allows you to create movies or take pictures and store them on the computer instead of on tape or film. OUTPUT DEVICES An output device is any hardware component that conveys information to one or more people. Three commonly used output devices are a printer, a monitor, and speakers. A printer produces text and graphics on a physical medium such as paper. A monitor displays text, graphics, and videos on a screen. Speakers allow you to hear music, voice, and other audio (sounds).
- 9. RESTRICTED RESTRICTED 9 SYSTEM UNIT The system unit is a case that contains the electronic components of the computer that are used to process data. The circuitry of the system unit usually is part of or is connected to a circuit board called the motherboard. Two main components on the motherboard are the processor and memory. The processor also called a CPU (central processing unit) is the electronic component that interprets and carries out the basic instructions that operate the computer. Memory consists of electronic components that store instructions waiting to be executed and data needed by those instructions. Although some forms of memory are permanent, most memory keeps data and instructions temporarily, which mean its contents, are erased when the computer is shut off.
- 10. RESTRICTED RESTRICTED 10 STORAGE DEVICES Storage holds data, instructions, and information for future use. For example, computers can store hundreds of millions of customer names and addresses. Storage holds these items permanently. A computer keeps data, instructions, and information on storage media. Examples of storage media are USB flash drives, hard disks, optical discs, and memory cards. A storage device records (writes) and/or retrieves (reads) items to and from storage media. Drives and readers/writers, which are types of storage devices, accept a specific kind of storage media. For example, a DVD drive (storage device) accepts a DVD (storage media). Storage devices often function as a source of input because they transfer items from storage to memory. A USB flash drive is a portable storage device that is small and lightweight enough to be transported on a keychain or in a pocket. The average USB flash drive can hold about 4 billion characters. You plug a USB flash drive in a special, easily accessible opening on the computer. A hard disk provides much greater storage capacity than a USB flash drive. The average hard disk can hold more than 320 billion characters. Hard disks are enclosed in an airtight, sealed case. Although some are portable, most are housed inside the system unit. Portable hard disks are either external
- 11. RESTRICTED RESTRICTED 11 or removable. An external hard disk is a separate, freestanding unit, whereas you insert and remove a removable hard disk from the computer or a device connected to the computer. An optical disc is a flat, round, portable metal disc with a plastic coating. CDs, DVDs, and Blu-ray Discs are three types of optical discs. A CD can hold from 650 million to 1 billion characters. Some DVDs can store two full-length movies or 17 billion characters. Blu-ray Discs can store about 46 hours of standard video, or 100 billion characters. Some mobile devices, such as digital cameras, use memory cards as the storage media. You can use a card reader/writer to transfer the stored items, such as digital photos, from the memory card to a computer or printer. COMMUNICATION DEVICES A communications device is a hardware component that enables a computer to send (transmit) and receive data, instructions, and information to and from one or more computers or mobile devices. Widely used communications devices modem and NIC. A modem is a communication device used to connect computers over telephone lines. A Network Interface Card (NIC) is used with cable to connect computers that are relatively close together such as those in the same building (Local Area Network LAN). Communications occur over cables, telephone lines, cellular radio networks, satellites, and other transmission media. Some transmission media, such as satellites and cellular radio networks, are wireless, which means they have no physical lines or wires.
- 12. RESTRICTED RESTRICTED 12 CHAPTER THREE COMPUTER CATEGORIZATION Industry experts typically classify computers in seven categories: personal computers (desktop), mobile computers and mobile devices, game consoles, servers, mainframes, supercomputers, and embedded computers. A computer’s size, speed, processing power, and price determine the category it best fits. Due to rapidly changing technology, however, the distinction among categories is not always clear-cut. This trend of computers and devices with technologies that overlap, called convergence, leads to computer manufacturers continually releasing newer models that include similar functionality and features. For example, newer cell phones often include media player, camera, and Web browsing capabilities. As devices converge, users need fewer devices for the functionality that they require. When consumers replace out dated computers and devices, they should dispose of them properly. PERSONAL COMPUTER A personal computer is a computer that can perform all of its input, processing, output, and storage activities by itself. A personal computer contains a processor, memory, and one or more input, output, and storage devices. Personal computers also often contain a communications device. Two popular architectures of personal computers are the Desktop Computers and the Mobile Computers. DESKTOP COMPUTERS A desktop computer is designed so that the system unit, input devices, output devices, and any other devices fit entirely on or under a desk or table. In many models, the system unit is a tall and narrow tower, which can sit on the floor vertically — if desktop space is limited. Some desktop computers function as a server on a network. Others, such as a gaming desktop computer and home theatre PC, target a specific audience. The gaming desktop computer offers high-quality audio, video, and graphics with optimal performance for sophisticated single-user and networked or Internet multiplayer games. A home theatre PC (HTPC) combines the features of a high-definition video/audio
- 13. RESTRICTED RESTRICTED 13 entertainment system with a desktop computer that is designed to be connected to a television and includes a Blu-ray Disc, digital video recorder, and digital cable television connectivity. These high-end computers cost more than the basic desktop computer. Another expensive, powerful desktop computer is the workstation, which is geared for work that requires intense calculations and graphics capabilities. An architect uses a workstation to design buildings and homes. A graphic artist uses a workstation to create computer-animated special effects for full-length motion pictures and video games. MOBILE COMPUTERS/MOBILE DEVICES A mobile computer is a personal computer you can carry from place to place. Similarly, a mobile device is a computing device small enough to hold in your hand. The most popular type of mobile computer is the Notebook computer. The following sections discuss the notebook computer and widely used mobile devices. Notebook Computers (Laptop) A notebook computer, also called a laptop computer, is a portable, personal computer often designed to fit on your lap. Notebook computers are thin and lightweight, yet they can be as powerful as the average desktop computer. A netbook, which is a type of notebook computer, is smaller, lighter than and often not as powerful as a traditional notebook computer. Most netbooks cost less than traditional notebook computers, usually only a few hundred dollars. An ultra-thin is another type of notebook computer that is lightweight and usually less than one-inch thick. Some notebook computers have touch screens, allowing you to interact with the device by touching the screen, usually with the tip of a finger. On a typical notebook computer, the keyboard is on top of the system unit, and the monitor attaches to the system unit with hinges. These computers weigh on average from 2.5 to more than 10 pounds (depending on configuration), which allows users to transport the computers from place to place. Most notebook computers can operate on batteries or a power supply or both. Tablet PCs Resembling a letter-sized slate, the Tablet PC, or tablet computer, is a special
- 14. RESTRICTED RESTRICTED 14 type of notebook computer that you can interact with by touching the screen with your finger or a digital pen. A digital pen looks like a small ink pen but uses pressure instead of ink. Users write or draw on a Tablet PC by pressing a finger or digital pen on the screen, and issue instructions by tapping on the screen. One design of Tablet PC, called a convertible tablet, has an attached keyboard. Another design, which does not include a keyboard, is called a slate tablet and provides other means for typing. Some Tablet PCs also support voice input so that users can speak into the computer. Tablet PCs are useful especially for taking notes in lectures, at meetings, conferences, and other forums where the standard notebook computer is not practical. MOBILE DEVICES Mobile devices, which are small enough to carry in a pocket, usually do not have disk drives. Instead, these devices store programs and data permanently on special memory inside the system unit or on small storage media such as memory cards. You often can connect a mobile device to a personal computer to exchange information between the computer and the mobile device. Some mobile devices are Internet-enabled, meaning they can connect to the Internet wirelessly. With an Internet-enabled device, users can chat, send e- mail and instant messages, and access the Web. Because of their reduced size, the screens on mobile devices are small, but usually are in colour. Popular types of mobile devices are smartphones and PDAs, e-book readers, handheld computers, portable media players, and digital cameras. Smart Phones and PDAs Offering the convenience of one-handed operation, a smart phone is an Internet enabled phone that usually also provides personal information management functions such as a calendar, an appointment book, an address book, a calculator, and a notepad. In addition to basic phone capabilities, a smart phone allows you to send and receive e-mail messages and access the Web usually for an additional fee. Some smart phones communicate wirelessly with other devices or computers. Many also function as a portable media player and include built-in digital cameras so that you can share photos or videos with others as soon as you capture the image. Many smart phones also offer a variety of application software such as word processing, spreadsheet, and games, and the capability of conducting live video conferences.
- 15. RESTRICTED RESTRICTED 15 Many smart phones have keypads that contain both numbers and letters so that you can use the same keypad to dial phone numbers and enter messages. Others have a built-in mini keyboard on the front of the phone or a keyboard that slides in and out from behind the phone. Some have touch screens, where you press objects on the screen to make selections and enter text through an on-screen keyboard. Others include a stylus, which is similar to a digital pen but smaller and has less functionality. Instead of calling someone’s smart phone or cell phone, users often send messages to others by pressing buttons on their phone’s keypad, keys on the mini keyboard, or images on an onscreen keyboard. Types of messages users send with smart phones include text messages, instant messages, picture messages, and video messages. · A text message is a short note, typically fewer than 300 characters, sent to or from a smartphone or other mobile device. · An instant message is a real-time Internet communication, where you exchange messages with other connected users. · A picture message is a photo or other image, sometimes along with sound and text, sent to or from a smart phone or other mobile device. A phone that can send picture messages often is called a camera phone. · A video message is a short video clip, usually about 30 seconds, sent to or from a smartphone or other mobile device. A phone that can send video messages often is called a video phone. A PDA (personal digital assistant), which often looks like a smart phone, provides personal information management functions such as a calendar, an appointment book, an address book, a calculator, and a notepad. A PDA differs from a smart phone in that it usually does not provide phone capabilities and may not be Internet-enabled, support voice input, have a built-in camera, or function as a portable media player. As smart phones and PDAs continue a trend of convergence, it is becoming increasingly difficult to differentiate between the two devices. This has led some manufacturers to refer to PDAs and smart phones simply as handhelds. E-Book Readers An e-book reader (short for electronic book reader), or e-reader, is a handheld device that is used primarily for reading e-books. An e-book or digital book, is
- 16. RESTRICTED RESTRICTED 16 an electronic version of a printed book, readable on computers and other digital devices. In addition to books, users typically can purchase and read other forms of digital media such as newspapers and magazines. Most e-book readers have a touch screen and are Internet-enabled. These devices usually are smaller than tablet computers but larger than smart phones. Handheld Computers A handheld computer, sometimes referred to as an Ultra-Mobile PC (UMPC), is a computer small enough to fit in one hand. Many handheld computers communicate wirelessly with other devices or computers and also include a digital pen or stylus for input. Some handheld computers have miniature or specialized keyboards. Many handheld computers are industry-specific and serve the needs of mobile employees, such as meter readers and parcel delivery people, whose jobs require them to move from place to place. Game Consoles A game console is a mobile computing device designed for single-player or multi-player video games. Standard game consoles use a handheld controller(s) as an input device(s); a television screen as an output device; and hard disks, optical discs, and/or memory cards for storage. Weighing on average between two and nine pounds, the compact size of game consoles makes them easy to use at home, in the car, in a hotel, or any location that has an electrical outlet. Three popular models are Microsoft’s Xbox 360, Nintendo’s Wii and Sony’s PlayStation. A handheld game console is small enough to fit in one hand, making it more portable than the standard game console. With the handheld game console, the controls screen, and speakers are built into the device. Because of their reduced size, the screens are small — three to four inches. Some models use cartridges to store games; others use a memory card or a miniature optical disc. Many handheld game consoles can communicate wirelessly with other similar consoles for multiplayer gaming. Two popular models are Nintendo DS Lite and Sony’s PlayStation Portable (PSP).
- 17. RESTRICTED RESTRICTED 17 SERVERS A server controls access to the hardware, software, and other resources on a network and provides a centralized storage area for programs, data, and information. Servers can support from two to several thousand connected computers at the same time. In many cases, one server accesses data, information, and programs on another server. In other cases, people use personal computers or terminals to access data, information, and programs on a server. A terminal is a device with a monitor, keyboard, and memory. MAINFRAMES A mainframe is a large, expensive, powerful computer that can handle hundreds or thousands of connected users simultaneously. Mainframes store tremendous amounts of data, instructions, and information. Most major corporations use mainframes for business activities. With mainframes, enterprises are able to bill millions of customers, prepare payroll for thousands of employees, and manage thousands of items in inventory. One study reported that mainframes process more than 83 percent of transactions around the world. Mainframes also can act as servers in a network environment. Servers and other mainframes can access data and information from a mainframe. People also can access programs on the mainframe using terminals or personal computers. SUPERCOMPUTERS A supercomputer is the fastest, most powerful and the most expensive of all computers. The fastest supercomputers are capable of processing more than one quadrillion instructions in a single second. With weights that exceed 100 tons, these computers can store more than 20,000 times the data and information of an average desktop computer. Applications requiring complex, sophisticated mathematical calculations use supercomputers. Large-scale simulations and applications in medicine, aerospace, automotive design, online banking, weather forecasting, nuclear energy research, and petroleum exploration use a supercomputer.
- 18. RESTRICTED RESTRICTED 18 EMBEDDED COMPUTERS An embedded computer is a special-purpose computer that functions as a component in a larger product. Embedded computers are everywhere — at home, in your car, and at work. The following list identifies a variety of everyday products that contain embedded computers. Consumer Electronics: Mobile and digital telephones, digital televisions, cameras, video recorders, DVD players and recorders, answering machines. Home Automation Devices: Thermostats, sprinkling systems, security monitoring systems, appliances, lights. Automobiles: Antilock brakes, engine control modules, airbag controller, cruise control. Process Controllers and Robotics: Remote monitoring systems, power monitors, machine controllers, medical devices. Computer Devices and Office Machines: Keyboards, printers, fax and copy machines. Because embedded computers are components in larger products, they usually are small and have limited hardware. These computers perform various functions, depending on the requirements of the product in which they reside. Embedded computers in printers, for example, monitor the amount of paper in the tray; check the ink or toner level, signal if a paper jam has occurred, and so on.
- 19. RESTRICTED RESTRICTED 19 CHAPTER FOUR COMPUTER HARDWARE AND SOFTWARE COMPUTER HARDWARE Computer hardware includes all the electrical, mechanical, and the electronic parts of a computer. Any part that we can see or touch is the hard ware. Computer hardware includes System Unit Peripheral devices Input devices i.e. keyboard, mouse etc. Output devices i.e. Display Unit, printer etc. Storage devices like hard disk, floppy disks etc. Communication Devices COMPUTER SOFTWARE The functioning of the computer is not dependent on hardware alone. So, what else is required? It requires a set of instructions that tells the computer what is to be done with the input data. In computer terminology, this set of instructions is called a program and one or more programs are termed as software. Software used for computers may be of different types. Some of which are: Application Software System Software Application Software These are software especially suited for specific applications for example, Microsoft office suite, coreldraw, mavis, railway and airline reservation, billing, accounting or software which enables creation and storage of documents are termed as application software. System Software The Operating System manages the various 1/0 devices of the computer and enables the user to interact with the machine. The computer understands only machine language i.e. 0’s and 1’s. There has to
- 20. RESTRICTED RESTRICTED 20 be software which translates the user language into machine language. The software which does this translation is known as the system software. Examples of system software are compilers and interpreters. COMPUTER COMPONENTS AND PERIPHERAL DEVICES IN DETAIL PERIPHERAL DEVICES: These are computer components which communicate with the CPU (processor) but are not located directly on the motherboard. Some are linked by expansion cards in expansion slots on the motherboard or connected directly on the ports via a cable attached on them. Some peripherals and major components of the computer are outlined and discussed below: KEYBOARD: A computer keyboard closely resembles a typewriter keyboard. It has additional keys to handle special functions required by a computer. A computer keyboard has three categories of keys: Alphanumeric Keys (Alphabet & Numeric). Special purpose keys. Function keys. Alphanumeric keys Comprises of alphabets (A-Z), numbers (0-9) and other characters. Special keys They perform specific functions. Special keys are Enter (return), Backspace, Insert, Delete, Home, End, Page-Up (PgUp), Page-Down (PgDn), Num-Lock, Caps Lock, Shift, Alt (Alternate), Ctrl (Control), Esc (Escape) and Cursor (Arrow) keys. The Shift key when pressed with another key; alters the meaning of any alphanumeric key for e.g. Shift with key 5 gives you ‘%’ The Ctrl and Alt keys when used with some other keys perform some special functions e.g. Ctrl, Alt and Del pressed together restarts the system. The Esc key is generally used to return to the previous menu or quit a program. The Cursor is a symbol displayed on the screen at the position where text or graphics will be inserted or deleted. The Cursor movement keys move the cursor on the screen. The Num-Lock is used to activate the numeric keys on the Numeric keypad.
- 21. RESTRICTED RESTRICTED 21 When Num-Lock is off the keys work like cursor movement keys. Scroll Lock is used to deactivate/activate scrolling of text on the screen. The Print Screen is used to print whatever is displayed on the screen. Enter or Return is used to communicate the end of an instruction or data being keyed in through the keyboard. Caps lock is used for keying upper case alphabets. Backspace is used to erase the character to the left of the cursor position. The Function keys are used to perform a set of operations using a single keystroke. The function keys can be defined as special purpose keys. In most of the software, pressing the F1 key will take you to the help feature. Other than these keys, 3 status indicators are present on the keyboard. They are Caps Lock on/off, Num-Lock on/off, Scroll Lock on/off indicators. There are two type of keyboard. Standard keyboard and Enhanced keyboard. a) Standard keyboard has functional keys from F1 to F10 (83/84 heavy or old school) b) Enhanced keyboard has functional keys F1 to F12 (101 – 104, 106 new similar to that of typewriter) MOUSE A mouse is an input devise which is used to points and select some options on the VDU. A mouse may have one, two or three buttons. The function each button depends on the program. When a user rolls the mouse across a flat surface, such as a desk, the screen cursor moves in the direction of the mouse’s movement. Clicking the mouse results in selecting an option. Positioning a cursor with the mouse is easier for non-typists than pressing various key combinations. With an appropriate software, a mouse can also be used to draw pictures. The Computer mouse is of three types and two classifications. The three types are: PS-2 mouse. USB mouse. Cordless mouse. The two classes are: Two Buttoned Mouse. Three Buttoned Mouse: The centre button has no use and sometimes can
- 22. RESTRICTED RESTRICTED 22 only be used for scrolling up and down. SCANNER There are a number of situations when some information (picture or text) is available on paper and is needed on the computer disk for further manipulation. A scanner is used for this purpose. A scanner scans an image and transforms it into graphics. These can be edited, manipulated and combined, and then printed. Scanners are used to reproduce photographs on the computer screen. These can be employed in training programs and in desktop publishing. Types of scanner a) Flat-bed scanner or desktop scanner b) Optic scanner, looks like a camera c) Hand held scanner PRINTER In order to get a copy of the output for later reference, you would require a printer. Printers are capable of printing at a very high speed. Two commonly used printers are the dot-matrix printer and the laser printer. Printers are classified on the basis of a number of parameters like, the mechanism used for printing, speed of printing, quality of output, direction of printing, and the kind of interface they have with the computer. Printers can be broadly classified as impact and non-impact printers. Let us understand this in detail. Impact Printers Impact printers work like typewriters. The characters are printed by striking the paper i.e., characters are printed by pressing a typeface against an inked ribbon a paper. Impact printers can again be classified as Character printers and Line printers. Character Printers Character printers print one character at a time. Examples of character printers are. Dot Matrix Printer and Daisy Wheel Printer.
- 23. RESTRICTED RESTRICTED 23 Dot Matrix Printer The most commonly used impact printer is the dot-matrix printer (DMP). In a DMP, tiny hammers or pins strike the ribbon to produce the desired characters. The print head consists of 9x7 arrays of pins. Characters to be printed are sent one at a time to the printer. The characters printed are a series of dots. Dot- matrix printers are inexpensive but noisy. They can print both text and graphics. They can print in any language without additional hardware change. They can also be made to print in colour by changing ribbons. These printers are used everywhere to produce internal reports and memos needed by organizations. Daisy Wheel Printer In a daisy wheel printer, each petal has a character embossed on it. A motor spins the wheel along with it. When the desired character spins to the correct position, a print hammer strikes it to produce a character. Line printers Line printers print one line at a time. Hence, line printers are generally faster than character printers. Printing speed varies from 150 lines to 2500 lines per minute. Some of the line printers are drum printers and chain printers. These can continuously print for a few hours. Drum printers A drum printer consists of a cylindrical drum. The characters to be printed are embossed on it. A set of print hammers one for each character in a line, are mounted in front of the drum. A character is printed by striking the appropriate hammer against the embossed character on the surface. The drum completes one revolution to print one line. The movement of the drum and the striking of the hammer must synchronize. Otherwise, the printing will not be uniform. As printer drums are costly they cannot be changed often. Chain Printer A chain printer has a steel band on which the characters are embossed. The band is rotated at a high speed. As the band rotates, a hammer is activated when the desired character comes in front of it. For every character there will be a hammer. Here also, the hammer movement and the chain movement must be synchronized. The main advantage of the chain printer is that its chain can be easily changed. Thus, different fonts and scripts can be used with the same printer.
- 24. RESTRICTED RESTRICTED 24 Non-impact printers: In non-impact printers, there is no contact between the typeface and the paper while printing. Some examples of the non-impact are laser printer, thermal printer, and inkjet printer. Laser Printer Laser printers print one page at a time. Laser printers use a light beam to form images on the paper using a toner ink as the medium. Laser printers are quiet workers. They produce very high quality output both text and graphics. They are typically used publishing. Other Non-impact printers The other types of non-impact printers are thermal printers (which use heat to print characters on paper) and inkjet printers (which use jets of ink to print characters on paper). These printers are not in use as much as the laser printers. PLOTTER A plotter is used to create high-quality visuals on paper, which a printer is incapable of doing. It can be used to create presentation-charts, graphics, tables and high quality technical drawings. There are two types of plotters: Drum and Flat Bed plotter. Drum Plotter The paper is placed over the drum that rotates back and forth. A carriage holding one or more pens is mounted horizontally across the drum. The carriage with the pens moves horizontally over the paper. Each pen could be filled with different colours. This plotter has the ability to produce colour pictures. Flat Bed Plotter In flat bed plotter, the paper does not move. The carriage holding the pens should provide all motions. Inkjet plotters can also produce large drawings with different colours. SYSTEM UNIT The processing part of the I-P-O cycle takes place in the system unit. The system unit consists of primary storage, arithmetic-logic unit, and the control unit. The arithmetic-logic and control sections together make up the central processing
- 26. RESTRICTED RESTRICTED 26 CENTRAL PROCESSING UNIT (PROCESSOR) The central processing unit (CPU) contains electronic circuits that cause processing to occur. The CPU interprets instructions to the computer, performs the logical and arithmetic processing operations, and causes the input and output operations to occur. It is considered the “brain” of the computer. ARITHMETIC-LOGIC UNIT (ALU) All calculations are performed in the arithmetic section, Operations like comparing takes place in the logic section of the CPU. CONTROL UNIT The control section of the CPU controls and directs the operation of the entire system. It acts like the central nervous system for all the components though; it does not process any data. PRIMARY STORAGE Primary storage is used for four purposes. To store the input data until the CPU is ready for processing. As a working storage space like a sheet of paper used for calculations. As an output storage area that holds the finished results. As a program storage area that stores the processing instructions. These separate areas are not fixed. The size of each area varies from application to application. Primary storage consists of RAM, ROM, and cache First of all you need to understand how the memory of a computer is organized. The computer can work with two states ON and OFF. ON state is represented by 1 and OFF state is represented by 0. This system of using 1’s and 0’s is called as the binary system. A ‘0’ or a ‘1’ is called a bit. A collection of 8 bits is known as a byte. The computer’s internal memory is organized as a collection of bytes. The size of
- 27. RESTRICTED RESTRICTED 27 memory available is measured in Kilobytes (KB) or Megabytes (MB). One Kilobyte represents 1024 bytes and one Megabyte represents 1024 Kilobytes. The computer uses three types of memory:- the RAM, the ROM and Cache. Ram Random Access Memory (RAM) is the area that is used for holding the programs and their data while the computer is working with them. RAM means the memory can be read from and written to randomly. The RAM is also known as short term memory because once the power is switched off all data in the RAM is erased. Common types of boards that hold memory chips SIMMs (single inline memory modules) DIMMs (dual inline memory modules) RIMMs (memory modules manufactured by Rambus, Inc.) Rom
- 28. RESTRICTED RESTRICTED 28 It contains permanently recorded instructions that are vital for starting up a computer. Instructions in ROM can be read but cannot be changed, hence the name Read-Only Memory. Further, these instructions are not erased when power goes off One set of instructions found in the ROM is called the ROM-BIOS which stands for Read Only Memory Basic Input Output Services. These sets of programs perform the most basic control and supervisory operations for the computer. Cache Memory A computer’s CPU is a fast device. But the storage devices are not as fast as the CPU. Most of the time the CPU has to slow down because of these devices. A small section of the high speed RAM is used to keep frequently needed information. SECONDARY STORAGE Computer’s primary storage or main memory is volatile and expensive. So, one need some storage device to store data and other information. It should be cheap and should not lose the content when power is switched off. This storage is called as the secondary storage. All secondary storage devices act both as input and output devices. Magnetic storage media fulfils these requirements and most common storage devices are disks and tapes. Floppy Disk It is the most common storage media and it helps transferring the data from one computer to another. Floppies are classified based on their storage density and data storage sides as: Single Sided Double Density (SSDD) Single side High Density (SSHD) Double Sided Double Density (DSDD) Double Sided High Density (DSHD) A diskette is divided into a series of concentric circles called tracks and within that into sectors. Data is stored in these sectors. Each piece of data that is stored, has a track number, a sector number and side number as an address. So data can be accessed randomly from anywhere on the disk. Hence, it is also called as Random Access storage.
- 29. RESTRICTED RESTRICTED 29 Hard-Disk The capacity of a hard-disk is higher than that of a floppy. The most significant difference between a floppy disk and a hard disk is that the hard-disk is completely sealed and is protected from dust and airborne particles. The name hard disk comes from the rigid platter that is inside the drive. This is, often called by different names like fixed disk or Winchester disk. The hard disk comes in different shapes. Most hard disks nowadays store something close to 500 MB. A hard disk has: Platters to store data Heads to read and write data from the platters. A motor to rotate the platters An electronic controller card that monitors the unit. Magnetic Tapes Apart from using disks for external storage purposes, magnetic tapes are also used for storing large amount data. The magnetic tape could be a large reel or a small cassette. The tape is essentially a plastic ribbon coated with some material that can be magnetized. The data is recorded on these magnetic spots. The data on the tape can however be read or written sequentially only. Hence, it is called as sequential access storage. THE MOTHERBOARD Largest, most important circuit board in the computer, it contains the CPU, with which all devices must communicate: Installed directly on the motherboard Linked by a cable connected to a port on the motherboard Indirectly linked by expansion cards It is also called the main board or system board The motherboard as the mother of all boards on the system comprises the following hardware connected on it: The Processor, Disk Drive: Hard disk, Floppy disk drive, CDROM drive VGA card / port
- 30. RESTRICTED RESTRICTED 30 I/O card / port Modem card / port TV card Sound card / port ALU Arithmetic logical unit, CU (control unit MU (Memory unit).
- 31. RESTRICTED RESTRICTED 31 Major Components on All Motherboards For processing: CPU Chip set For temporary storage: RAM Cache memory Electrical system: Power supply connections For communication with other devices: Buses Expansion slots Programming and setup data: Flash ROM CMOS setup chip NOTE: THE BUS: A computer bus technology is a technology that provides means of transmitting data from one part of the computer to another part of the computer. The computer bus connects all devices to the computer CPU and
- 32. RESTRICTED RESTRICTED 32 main memory. The computer bus consists of two parts, the address bus and a data bus. The data bus transfers actual data, whereas the address bus transfers information about where the data should go. THE CMOS: Stores setup (configuration) information. THE FLASH ROM: Holds software needed to start up PC and begin loading an OS. Visual Display Unit (VDU) This looks like a TV screen and is used to display information. VDUs can work in two different modes viz. Text mode and graphic mode. In text mode, the screen is divided into a matrix of rows and columns; each cell of the matrix is used for one character. A typical screen has 80 character positions per line and 25 lines across the screen. In graphic mode, the screen is treated as an array of tiny dots called pixels. The characters and pictures that appear on the screen are shown by making a drawing of these pixels. The number of dots on the screen is called as resolution. The higher the resolution the better the picture. A typical high resolution monitor has 1024 x 768 pixels across the screen. Further, a VDU can be a Colour VDU or a Monochrome depending on the video mode. The formation of images on the screen is handled by the Video Controller. The Video Controller along with the memory that holds the display- data are together referred to as display adaptors. Some examples of adaptors are Monochrome Graphics adaptor (MGA), Hercules Graphics Adaptor (HGS), Super Video Graphics Array (SVGA). SYSTEM UNIT IN DETAIL Now that you are aware of the overall design of a computer system you can go into little more detail about each component inside your system unit. Though these details do not affect you as an end user, it completes your knowledge of the computer. System Unit It is a box like structure of the computer. Inside this box you can find the power supply, storage device, hard disk and floppy drives, and the motherboard containing CPU and memory. It also contains expansion slots and cards to
- 33. RESTRICTED RESTRICTED 33 connect various input and output devices. It can also contain optional cards like the modem card, mouse card, video card, sound card. System unit or Main unit or Console comes in two styles. Desktop model and Tower model. Outside The Main Unit Indicators Power on indicator: it glows when the power is on. Hard disk activity indicator: this gives the information as to whether the hard disk is being accessed (read from or written to) or not. Power switch Depending on the model of the computer, power switch can be anywhere. Reset switch Pressing this switch restarts your computer, your power supply. Inside The System Unit The Internal Power Supply One of the main components inside the system unit is the power supply. The Microprocessor The CPU or the main microprocessor is the most important chip on the motherboard. The entire design of the PC is based on this chip. The computer’s performance depends directly on the CPU. The performance of CPU depends on the model, version and speed. Model Each CPU has a specific model number assigned to it. Given below is the list of common CPUs produced by Intel Company in an increasing order of their power, speed and performance. 80386, 80486, 80586 or Pentium. Version In each Model of CPU you may find further variations, such as SX, DX, DX2 etc. In this, SX is less powerful than DX and DX is less powerful than DX2. Speed The speed is measured in Megahertz. Higher the value, faster is the information processed by CPU.
- 34. RESTRICTED RESTRICTED 34 Clock All components should work in perfect synchronization, for the computer to produce the desired results. The clock provides the timing signals in the form of pulses that are used by the computer components to synchronize their work. The clock chip uses a quartz crystal. The speed of the clock is measured in MHz. Speed of Operation Speed of a computer can be assessed either in terms of the processing capacity of the microprocessor or by the speed of the computer which is measured in MIPS (Million Instructions Per Second). 80386 Model can process 32 bits at a time, has a clock speed of 33 MHz and has a speed of 0.4 MIPS. The Memory The internal memory of the PC is in the form of chips. The Bus Communication between the microprocessor, the memory chips, and another chips found on the motherboard is accomplished a set of wires running between them. This set of wires is called the bus. The Ports As in human terminology, ports are used to receive and send goods. Similarly, the I/O devices like the keyboard, the printer etc. are connected to the system unit through ports. These ports could be serial or parallel. A serial port, is one where eight bits queued up and sent bit. In the parallel port all the eight bits are transferred simultaneously. The Storage System The hard disk drive and floppy diskette drive are also mounted in the system unit. HOW DOES A SYSTEM START? The Start-Up Process Every time a computer is switched on, it goes through a series before the user is permitted to interact with it. Stored in the ROM is a set of instructions that check each functional areas of
- 35. RESTRICTED RESTRICTED 35 the computer. These instructions are called the power on self-test (POST) program. Forms a part of the ROM-BIOS. The POST checks the entire RAM area and tests the connections to the various hardware devices attached, like the keyboard, the disk drive, etc. If problem occurs with any of the connections to the hardware devices or with the RAM, POST program reports this on the screen. The Bootstrap Process Once the POST is over the next stage is called the ‘bootstrap’ process. Now the computer waits for the operating system to take over. In the BIOS itself, there is small program called the bootstrap loader, which copies the Operating System from the floppy or hard disk to the RAM. The bootstrap loader first checks the A drive for a bootable disk. (A disk that has the Operating System is a bootable disk). If the disk in that drive is not bootable, errors are reported. If the floppy is not there in the drive, the hard disk drive is checked. If the hard disk also does not have the operating system then the computer reports ‘Boot disk failure’. This process of loading or copying the operating system is called booting. Soft Boot and Hard Boot The Computer system can be restarted by pressing the keys <Ctrl>, <Alt>, and <Del> simultaneously. This is known as a soft boot. Using the reset switch or switching off and then switching on the computer is known as a hard boot. Connecting your Computer You must first comprehend the two main steps needed to get your PC working. They are: Connecting the sytem unit, monitor, printer to the power supply. Connecting the various components, etc., the monitor (VDU). Keyboard, mouse, and printer to the system unit. Before making connections, make sure that the power supply to the PC, printer and monitor is off, Connecting your system while the power is on may cause permanent damage to the computer and its peripherals. Keyboard-System Unit Connection Plug the keyboard into the circular keyboard socket (also called a port or
- 36. RESTRICTED RESTRICTED 36 interface in computer jargon) on the rear panel. The position of the keyboard socket on your system may be different. Before inserting the cable, make sure that the pin in the cable are lined up with respect to the holes in the connector. Make sure the keyboard plug is firmly fitted in the keyboard socket. Monitor-System Unit Connection Monitor has two cables. One is connected between the monitor and computer, referred to as the video cable. The other cable is connected between monitor and power socket called the power cable. The power outlet may be present on the rear panel of the system unit, in which case the power plug must be connected to this outlet. Otherwise, it should be connected to the main power supply. The video cable will go into the respective socket only. Generally, in all the PCs this socket is marked as ‘MON’. Mouse-System Unit Connection The rear panel of a system unit has both serial and parallel ports. The serial ports are numbered as COM1, COM2 ... and parallel ports are numbered as LPT1, LPT2, A mouse could be a serial port mouse or a parallel port mouse. You will have to connect it accordingly. Connecting a mouse to the machine is not enough. A dedicated program called the Driver which comes with the mouse has to be executed as per installation procedures given in the accompanying manual. Printer-System Unit Connection Printer unit has two cables. One is connecting the printer to the computer and another connecting it to the power supply. Printers are of two types: - Serial and Parallel. Your printer manual will tell you what kind of printer you have. One end of the printer cable will be connected to the appropriate port on the real panel. The other end of the cable has to be connected to the printer. The connector is tapered so that you can only connect the cable one way. Normally, you will find small wire clamps on either side of the port to hold the connector securely. With the cable connected, press the wire clamps into the notches.
- 37. RESTRICTED RESTRICTED 37 Power Connection It is better to connect the PCs to some constant power supply device. This is required to avoid any damage that could be caused because of power fluctuations. The commonly used protection devices are Voltage Stabilizers, Constant Voltage Transformers (CVTs), and Uninterrupted Power Supplies (UPSs). In case, you have a CVT or an UPS; connect your computer’s power cable to the CVT or UPS. The CVT’s power cable in turn is to be connected to the mains. Operating your Monitor The ON/OFF switch is used to switch on/ switch off the monitor. A monitor has a light indicator to show whether it is on or off. The brightness and contrast control knobs are used to adjust the brightness and sharpness of the text or image on the screen, respectively (similar to the controls present on a TV). Some monitor also have knobs to position the image at the centre of the screen, these are the vertical shift and horizontal shift knobs used to shift the image vertically and horizontally, respectively. When you are satisfied that everything is working as it should, turn the power switch off to stop the test. Maintaining your Computer To keep your computer system working properly, it is necessary to protect the hardware from environmental hazards, unreliable power supply and natural calamities. The following are some dos and don’ts for a computer and its components. General Precautions Points to be borne in mind while using your PC: Do Keep your computer system in a cool, dry, and dust-free environment. Ensure that the power switches on the system unit, monitor and printer are OFF before switching on the mains. Switch off the monitor, system unit and the printer, before switching off the mains.
- 38. RESTRICTED RESTRICTED 38 Clean the computer work area every day. Keep your system away from room walls to ensure proper air flow around the computer. Do Not Allow eating or drinking near the computer. Smoke in the vicinity of your computer. Allow direct sunlight to fall on your computer. Run any electric equipment like a vacuum cleaner in the vicinity of the computer when it is on. Maintaining your System Unit Do Park the hard disk before shifting the machine, when the unit needs to be transferred from one site to another. Parking refers to positioning the disk head on an unused area to ensure that the head does not damage the disk. Handle the floppy drive lever gently. Ensure that there is no diskette, flash drive or external storage device connected to the computer before switching on or off the system unit. Do Not Switch on the system with an external storage device connected to the computer. Switch off the system when the hard disk drive is active, i.e. when the indicator is glowing. Maintaining Your Keyboard Do Clean the keyboard regularly. Use a vacuum cleaner keyboards as it can extract the dust collected between the keys. Do Not Strike the keys hard as those of a manual typewriter since these keys are soft touch. Rest your hands on the keyboard.
- 39. RESTRICTED RESTRICTED 39 Keep anything on the keyboard. Use the keys after switching off the system. Stretch the keyboard cable.