What is the Meaning of Computer Hardware?

COMPUTER HARDWARE

The hardware elements of a computer are generally grouped into four major categories namely:

·   Input devices

·   The Central Processing Unit (CPU)

·    Output devices

·   Secondary Storage devices

INPUT DEVICES

Input devices are computer hardware that translates data from human readable into a form that the computer can process. In other words, input devices allow people to put or enter data into the computer in a form the computer can use. The human-readable form may be words like the ones in these sentences but the computer-readable form consists of binary 0s and 1s, or on and off signals.

Input devices can be classified according to how they are used to enter data. These include:

·  Keying devices

·  Pointing devices

· Scanning devices

·  Speech/Voice recognition devices

·  Digital devices

Keying devices

Keying devices are input devices are input hardware that convert numbers and other characters into machine readable from. Keying devices include keyboard and keypad. Key pads are found on devices such smart phones and ATMs (Automatic Teller Machines).

Because keying devices require typing by people, the data input this way is less accurate than data input via non-keyboard source data entry devices.

Pointing devices

One of the most natural of all human gestures is the act of pointing. This concept is incorporated in several kinds of input devices. The pointing devices used with microcomputers are the mouse, the trackball, the joystick and the touchpad all of which have variations. All pointing devices have the same purpose; allowing the user to move the cursor (or pointer) around the screen and to click to select items or perform other functions.

Mouse

A mouse is a device that is rolled about on a desktop to direct a pointer on the computer’s display screen. Its name is derived from its shape, which looks a bit like a mouse, its connecting wire that one can imagine to be the mouse's tail, and the fact that one must make it scurry along a surface. When you move the mouse on the desktop, the pointer on the screen moves in the same direction.  The mouse pointer is the symbol that indicates the position of the mouse on the display screen. The pointer will change from an arrow to a pointing finger icon depending on the task you are performing. It also changes to the shape of an I-beam to indicate where text or other data may be entered.

Mice contain at least one button and sometimes as many as three, which have different functions depending on what program is running. Some newer mice also include a scroll wheel for scrolling through long documents. The movement of the mouse over a flat surface is mirrored by a pointer on the monitor screen. Buttons on the mouse allow you to make selections from the menus, move objects around the screen and paint or draw.

Types of Mice

Mechanical Mice

Mechanical mice use a rubber-coated ball that contacts the mouse pad. Moving the mouse causes the ball to move, which in turn causes one or both of the internal cylindrical rollers with which the ball is in contact to move.

Advantages

·   Mechanical mice are inexpensive.

Disadvantages

· They require frequent cleaning since the ball can get dirty. Dirt causes the mouse pointer to move erratically.

·   They provide limited resolution

·  They are unreliable because of many moving parts

Optical Mice

Optical mouse uses an optical sensor instead of the mouse ball. It emits a small beam of red light which bounces off the surface into a sensor. The sensor sends co-ordinates to the computer which in turn moves the cursor or pointer on the monitor screen, according to these co-ordinates.

Advantages

·   Do not require frequent cleaning as mechanical mice.

·   More reliable because of the reduced number of moving parts

·  Can slide over most surfaces since it does not have a ball.

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Disadvantages

· They are more expensive than mechanical mice

Cordless Mouse

The cordless mouse uses the wireless communication technology (via infrared, radio or Bluetooth) to transmit data to the computer. And like the wireless, it doesn’t use any cord.

Mouse Terminology

The terms you are most likely to encounter when using a mouse or a trackball are as follows:

Point                 To move the pointer to the desired spot on the display screen such as over a particular word or object.

Click               Tap – that is press and quickly release the left mouse button. A click often selects an item on the display screen.

Double Click  Tap – press and release the left mouse button twice in quick succession. A double click often opens a document or starts a program.

Right Click    Tap – press and release the right mouse button. Right clicking brings up a pop-up menu with options available to the object over which the cursor is positioned.

 Shift Click    Press and release the left mouse button while holding the Shift key down. Shift clicking enables you to select multiple items.

Drag                 Press and hold the left mouse button while moving the pointer to another location.

Drop                 Releasing the mouse button after dragging

Trackball

Another pointing device, the trackball is a variant on the mouse. A trackball is a movable ball on top of a stationary device that is rotated with the fingers or palm of the hand. A trackball looks like a mouse turned upside down. To move the pointer, you rotate the ball with your thumb, your fingers, or the palm of your hand. There are usually one to three buttons next to the ball, which you use just like mouse buttons.

The touchpad

The touchpad contains a touch-sensitive pad and is normally found on laptops. It is a pressure- and motion-sensitive flat surface about the same size as a mouse over which you move your fingers to control the cursor/pointer on the screen. Buttons placed close to this surface allow for selection of features on the screen.

The Pointing Stick

A pointing stick is a pointing device first developed by IBM for its notebook computers. Most pointing sticks are pressure-sensitive, so the pointer moves faster when more pressure is applied. The pointing stick found on laptop computers looks like a pencil eraser. It protrudes from the keyboard between the B, G and H keys. Pushing on the pointing stick with your finger will move the pointer around the screen. Once again, buttons placed close by allow for selection of features on the screen.

Joysticks

A joystick is an input device consisting of a stick which lets you control the movement of an object on the screen by operating a small lever. It is used mainly for computer games such as flight simulators and occasionally for CAM/CAD systems. Special joysticks are also available for people with disabilities that don’t let them use a mouse or a trackball.

Light pen

The light pen is a light-sensitive stylus or pen-like device connected by a wire to the computer terminal. It allows you to point and make selections more accurately on a screen. The tip of the light pen contains a light-sensitive element which, when placed against the screen, detects the light from the screen and enables the computer to identify the location of the pen on the screen. Making selections with a light pen is far more accurate than using your finger to make selections on a touch sensitive screen. Light pens also allow the user to draw directly on the screen. However, they are not as accurate as a digitising tablet and drawing can become uncomfortable.

Digitising tablet (graphics tablet)

A digitising tablet is a board which can detect the position of a pointing device such as a stylus or a puck on its surface. A stylus is a pen-like pointing device for a user sketches an image on the graphics/digitising tablet. A puck is a copying device with which the user traces or copies an image. The images the user sketches are displayed on the computer screen. Digitizing tablets are used primarily in graphics design, computer animation and engineering.

Pen-Based Systems

Pen-based computer systems use a pen-like stylus to enter handwriting and marks into a computer. Small handheld computers called PDAs (Personal digital assistants) use pen-based input.

Touch Screens

A touch screen is a video display screen that has been sensitized to receive input from the touch of a finger. Behind the screen, which is covered with a plastic layer, there are invisible beams of infrared light. The user can input a request for information by pressing on displayed buttons and then see the requested information displayed as output on the screen.

Touch screens are often used in automatic teller machines, in directories displaying tourist information in airports and hotels, in fast-food restaurants to select menu items and in preschool multimedia education.

SOURCE-DATA (DIRECT) ENTRY

Source-data input devices do not require keystrokes to input data to the computer. Data is entered from as close to the source as possible; people do not need to act as typing intermediaries. Source-data entry devices include scanning devices, voice recognition input devices and digital input devices

Scanning Devices

Scanners are input devices that use laser beams and reflected light to translate hardcopy images of text, drawings and photos into digital form. The images can then be processed by a computer, displayed on a monitor, stored on a storage device, or communicated to another computer.  Scanning devices can be classified according to the technology they use to capture data. These are optical scanners magnetic scanners.

Magnetic Scanners

Magnetic scanners capture by using magnetic technology. Magnetic scanners include: magnetic-ink character recognition (MICR) and magnetic stripe.

Magnetic-Ink Character Recognition (MICR)

Magnetic-Ink Character Recognition (MICR) is a scanner that translates the magnetically charged numbers printed at the bottom of bank cheques and deposit slips. MICR characters, which are printed with magnetized ink, are read by MICR equipment, producing a digital signal. This signal is used by a bank’s reader/sorter machine to sort cheques.

MICR is mainly used in the banking industry to read/sort cheques. Bank cheques have the following information encoded in them:

• The cheque number

• The bank branch number

• The customer’s account number.

Magnetic stripe codes

A magnetic stripe is a short length of magnetic coated tape printed on the surface of or sealed into a ticket or card. It contains information to identify the ticket or card and its user.

The card is read by swiping it – moving the magnetic strip through a reader so that the strip can be read. Such stripes are found on bank cards which identify the card holder’s bank account, so that the card holder can perform banking transactions.

Cards with these magnetic stripe codes can provide quick identification of people entering buildings, allowing access to the card holder. These cards are therefore used for security purposes too. Examples of other uses are in phone cards and debit cards for cell phones. The magnetic stripe in this instance contains information about the amount of money left ‘on’ the card.

Optical Scanners

Optical scanners capture data using light. A special type of concentrated light is passed over the object, image or text that needs to be input. These types of scanners include: image scanners, Optical Character Recognition (OCR), Optical Mark Recognition (OMR) and Bar-Code Readers.

Image ((Graphics) Scanners

Image scanners are scanners that convert text, drawings and photographs into digital form. They were originally designed to scan pictures (image scanners) but now their use is extended, for example to scan text into a word processing program. Image scanners are used in document management, desktop publishing (DTP), and multimedia development.

There are many types of scanners:

    · Flat-bed scanner: This is a type of optical scanner that consists of a flat surface on which you lay documents to be scanned. Flatbed scanners can scan single sheets and book-bound pages. The picture is placed on a flat scanning surface and the image is captured, similarly to how a photocopying machine works.

·   Hand-held scanner: This is a type of scanner that is rolled by hand over the documents to be scanned. These scanners are generally used to scan in small images or parts of images. Their resolution is not very high.

·   Drum scanner: This is a type of scanner used to scan one sheet at a time. They cannot handle book-bound pages.

·    Sheet-fed scanner: This is a scanner that allows only paper to be scanned rather than books or other thick objects. The sheet that contains the image is fed through rollers and the picture is scanned as the paper passes through.

Optical Mark Reader (OMR)

Optical Mark Recognition (OMR) uses a device that reads pencil/soft pen marks and converts them into computer usable form. OMR technology scans a printed form and reads predefined positions and records where marks are made on the form.

OMR detects the position of black marks on white paper. The documents to be read have empty boxes pre-printed on them. The user makes pencil or ink marks in the appropriate boxes. The intensity of the reflected light from these marks on the form is detected by the OMR. This is sometimes called mark sensing. The computer records the position of the marks and analyses it to determine the meaning of the data. OMRs are used mainly in assessing multiple-choice examinations such as Kenya Certificate of Primary Education (KCPE), questionnaires given out by researchers or ballot papers.

This technology is also useful for applications in which large numbers of hand-filled forms need to be processed quickly and with great accuracy, such as surveys, reply cards, questionnaires and ballots.

Optical Character Recognition (OCR)

OCR (optical character recognition) uses a device that reads special OCR character set called fonts as well as typewriter and computer-printed characters and converts them into machine-readable from. Some advanced OCR systems can recognize human handwriting but the letters must be block printed.

Examples that use OCR characters are utility bills and price tags on department-store merchandise.

 OCR is being used by libraries to digitize and preserve their holdings. OCR is also used to process checks and credit card slips and sort the mail.

Barcode readers

A barcode is a set of vertical lines of differing thickness with a string of numbers printed at the bottom found on most manufactured and retail products. You can see barcodes on items in supermarkets, books in libraries and on such things as magazines. The barcode is read by an optical scanner (barcode reader) in which a laser beam scans the barcode and the light is reflected back into the scanner. The information received by the scanner is sent to a computer for processing.

Barcodes form part of the Point of Sale (POS) system usually found at retail outlets. A terminal is connected to a central computer which records details after the barcode of an item has been scanned. The price of the product is displayed on a monitor at the point of sale. Meanwhile the central computer calculates the amount due, including VAT, and prints an itemised receipt. The information recorded can also be used for stock control and sales analysis.

Radio frequency identification (RFID) uses radio waves as a means of identifying animals, persons and objects. A chip connected to a small antenna makes up the RFID transponder or RFID tag. Information such as a serial number is transmitted to an RFID receiver that converts the radio waves to digital information so that it can be processed by the computer.

RFID chips are used for tracking animals, for example, as they can be embedded in the skin of the animal and the tag can be read once the animal is within range of the reader. Some stores are now tagging their merchandise with RFID tags to record POS information, and also as a means of security to reduce theft. Alarms can be raised when someone tries to exit a store without paying for an item.

Smart cards

In recent years, new means of storing data on cards have become available. ‘Smart’ cards with very thin gold-coloured memory chips sealed into them can store more information than magnetic stripe cards. Data is stored on the memory chip embedded in the card, allowing a greater amount of information to be kept and updated on the card than would be the case with the old-style magnetic stripe. The chips can hold information for cell phone use, debit and credit cards, and any prepaid services. Eventually, smart cards may store information about a person’s driving history, their birth certificate or paper, and could even be imprinted with the holder’s voice, fingerprints and retinal scans.

Optical Cards

These are plastic, laser recordable, wallet-type cards used with optical card readers. They can store much more data than smart cards and may become more popular in future.

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Audio and video input devices

Voice data entry/voice recognition

Voice recognition systems require the use of a microphone. This system accepts the spoken word as input data or commands. Human speech is very complex, because it carries tones, inflections and emphasis of various parts of words and phrases. The computer is programmed to recognise certain patterns of speech. Using a microphone, human speech is coded into a sequence of electronic signals. These signals are compared to a set of stored patterns. If they match, the command or data being entered is accepted by the computer and is processed.

Simple commands can be used to control machines or even ‘type’ letters in a word processor. Voice recognition has become important in many areas of our lives. It has made life easier for people with movement difficulties, such as the paralysed, who with suitable equipment can now operate a wheelchair, lighting and even open doors using voice commands.

Sound capture

All modern computers contain a built-in microphone for sound capture. This means that you can record your voice, for example, to make comments that are embedded in a word processing document. A sound card on your computer is required for recording voice or music. The sound card digitises the information into a form that the computer can understand.

MIDI instruments

Electronic musical instruments can have a MIDI port (Musical Instrument Digital Interface) for input into the computer. The sounds are digitised and stored as a file, can be displayed on screen, edited and played back, using appropriate software.

Digital input devices

Digital cameras

Digital cameras capture an image and store it in memory within the camera. These cameras have a sensor that converts the light into electrical charges. The processor in the camera converts this information into digital data and stores it on a small diskette, flash memory or flash RAM card. The digital images can then be uploaded from the camera to a computer where they can be displayed, manipulated or printed. The memory can be erased so that more images can be captured. Unlike normal RAM memory where the information is lost when the computer is switched off, flash RAM is non-volatile. That is, the images are not lost when the camera is switched off. The resolution of the camera is measured in pixels. The larger the number of pixels the camera has, the clearer the image and the greater the detail captured.

Digital video camera (Digital video camcorder or DVD camcorder)

In the digital video camera, light is focused onto an image sensor called a charge-coupled device which contains thousands of light-sensitive diodes called photo sites. These detect the light intensity and record an image. The digital video camera/camcorder detects not only light intensity but also levels of colour to reproduce a coloured image. The camera takes many pictures per second to give an impression of movement.

Remote control

A remote control emits a beam of infra-red light that carries data signals. Commonly used for input to televisions, stereo systems, VCRs and DVD players, they are now being used by computers as a wireless means of communication.

Sensors

A sensor is an input device that collects specific kinds of data directly from the environment and transmits it to a computer. Although you are unlikely to see these devices connected to a computer, they exist all around us. Sensors convert chemical or physical changes in humans and their environment to electrical signals that can be passed to a computer, where it is analysed, stored and manipulated by special software. Sensors are useful in the fields of medicine, environmental planning and preservation, weather reporting, and so on. A variety of sensors can be used to measure such things as heat, light, sound, pressure, strain, acidity (pH), oxygen concentration, humidity, pulse, water level, water flow, speed, tilt or even something like a door or a valve opening or closing.

Human-Biology Input Devices

Characteristics and movements of human body when interpreted by sensors, optical scanners, voice recognition and other technologies can become forms of input. Examples include:

Biometric systems

Biometrics refers to the science of identifying an individual through their body characteristics such as face geometry and hand geometry (e.g. fingerprints), iris or retinal scans, veins and voice patterns. All these forms of identifying an individual can be input into a computer system set up for security purposes. In the near future they may become common, for allowing access to buildings and bank accounts. Retinal scans use a ray of light directed into the eye to identify the distinct network of blood vessels at the back of the eye. Fingerprint readers scan the imprint made by the pattern of ridges on the finger and compare it to a set of patterns stored in memory. Fingerprints are considered unique, as no two individuals have the same fingerprint.

Line-of-Sight Systems          

Line-of-sight systems enable a person to use his/her eyes to point at a screen. This technology allows users with physical disabilities to direct a computer. This is accomplished using a video camera mounted beneath the monitor in front of the viewer. When the user looks at a certain place on the screen, the video camera and the computer translate that location into screen coordinates.

Terminals

People working on a large computer system are usually connected to the main or host computer via terminals. A terminal is an input/output device that uses a keyboard for input and a monitor for output. There are two types of terminals:

·         Dumb: A dumb terminal can only be used to input data to and receive information from a computer system; it cannot do any processing on its own.

For example, airline clerks use dumb terminals at airport ticket and check-in counters.

·         Intelligent:  An intelligent terminal has built-in limited processing capability and RAM but does not have its own storage capacity. Intelligent terminals are not as powerful as microcomputers and are often found in local area networks where users share application software and data stored on the server. Examples of intelligent terminals include ATMs and Point-of-Sale (POS) terminals.

·         The Automated Teller Machines (ATM)

ATM is a terminal that reads the encoded magnetic stripe on the ATM card and provides output in the form of display on a monitor and printed records of transactions.

·         Point-of-Sale (POS) terminals

A POS terminal combines input capabilities of a cash-register-type keypad, an optical scanner for reading barcodes, and/or a magnetic stripe reader for reading credit cards with output capabilities of a monitor and a receipt printer. POS terminals are usually hooked up to a central computer for credit checking and inventory updating. POS terminals are found in most supermarkets.