The Concept of Computer Hardware 3


These are the physical aspect of the computer that you see and touch. There are three basic hardware components viz; input/output, central processing unit, and auxiliary hardware.

1. Input is any data or instructions you enter into the memory of a computer. Once input is in memory, the CPU (Central Processing Unit) can access it and process the input into output. 

Four types of input are data, programs, commands and user responses:

  • Data is a collection of unorganized facts that includes words, numbers, pictures, sounds and videos. A computer manipulates and processes data into information, which is useful.
  • A program is a series of instructions that tells a computer how to perform the tasks necessary to process data into information. Programs respond to commands issued by users. Programs are kept in storage media such as a floppy disk, hard disk, CD-ROM or DVD-ROM.

A user response is an instruction you issue to the computer by replying to a question posed by the computer program. An example can be Do you want to save the changes you made? If your answer is Yesto this question, the program saves your changed file on a storage device.

Output is data that has been processed into a useful form called information. This means a computer processes input into output. Computers generate several types of output, depending on the hardware and software being used and the requirements of the user. You may choose to display or view this output on a monitor, print it on a printer, or listen to it through speakers or a headset. Four common types of output are text, graphics, audio and video.

  • Text consists of characters that are used to create words, sentences and paragraphs. A character is a letter, number, punctuation mark, or any other symbol that requires one byte of computer storage space.
  • Graphics are digital representations of nontext information such as drawings, charts and photographs. Graphics can also be animated, giving them the illusion of motion. Animation is created by displaying a series of still images in rapid sequence.
  • Audio is music, speech, or any other sound. Recall that sound waves such as the human voice are analog. To store such sounds, a computer converts the sounds from a continuous analog signal into a digital format.
  • Video consists of images that are played back at speeds that provide the appearance of motion. Video is often captured with a video input device such as a video camera or VCR. Most video signals are analog: however, some video devices record the video images digitally.

They are hardware devices that send information into the CPU. Without any input device, a computer would simply be a display device and not allow users to interact with it, much like a TV. Below is a listing of different types of computer input devices.

  1. The Keyboard

      One of the main input devices used on a computer, a PC’s keyboard looks very similar to the keyboards of electric typewriters, with some additional keys. Today most users use the QWERTYstyle keyboards. Below is a graphic illustration of where each of the keys is on a U.S. QWERTY style keyboard.

A US QWERTY Keyboardlayout

Below is a graphic of the Saitek Gamers’ keyboard with indicators pointing to each of the major portions of the keyboard?

A Gamers Keyboard

Anatomy Of The Keyboard

Keyboard is among the input devices we use to enter data into the computer memory. The computer keyboard resembles the typewriter keyboard. It has 101/102 keys divided into five groups:

  • Typing keys 
  • Special keys 
  • Function keys 
  • Dedicated cursor keys 
  • Numeric key pad

When a key is pressed its corresponding character would appear on the screen. 

Typing Keys

These are the keys that contain the 26 letters of the alphabet 

Function Keys 

The function keys are labeled from F1-F12 of the keyboard and they are used for different purposes. These have different application programs depending on the software in use. E.g. in Microsoft windows F1 is generally for help, F2 for Renaming of an item, et.c they can also be combined with other keys to perform a specific function e.g. ALT + F4 closes a window. 

Shift Key 

This key cannot be used alone, it need to be paired with other keys to perform certain operation e.g. it can be used to enter upper and lower case character.

Control Key 

This key also doesn’t perform any function when used alone; it is used in conjunction with other keys on the keyboard to generate internal code on the system e.g. 

1. Ctrl + Ato select all characters 
2.Ctrl + BTo Bold selected text
3. Ctrl + CTo Copy selected item
4.Ctrl + ETo move an item to the centre of a page
5. Ctrl + FTo find a character within a page (s)
6. Ctrl + I To Italize characters
7.Ctrl + LTo move an item to the left side of a page 
8.Ctrl + NThis starts a new window
9.Ctrl + OTo open an existing document 
10.Ctrl + PTo printout a page
11.Ctrl + RTo move an item to the right 
12.Ctrl + STo save an item
13.Ctrl + UTo underline characters
14.Ctrl + VTo paste
15.Ctrl + WTo close a window
16.Ctrl + XTo Cut
17.Ctrl + ZTo undo an action.

The Alternate Key

It is also paired with other keys to give command e.g. ALT + F4 to close a window

Caps lock Key 

It is a toggle key that is On/Off key. It is used to change characters from lower case to upper case and vice-versa. When the caps lock key light is on all the characters are in the upper case and when the light is off the characters return to the lower case. 

The Enter Key

This key is similar to the carriage in typewriter it is also called return key or carriage. When it is pressed it will command the computer to execute a certain action 

Space Bar

This key is used to create space from left to the right 

Backspace Key

This key deletes characters from right to the left of the cursor.

Tab Key

This key is similar to the typewriter tab. The key shifts the cursor eight spaces to the right of current position. 

The Escape Key (Esc)

In MS-DOS it means the current line would be deleted. But as other meanings when pressed in other programs. It may exit the current activity and return to the previous, it also enables you to abandon error condition and resume to the activity prior to it.

Ctrl + Tab 

Pressing of these two keys will move the cursor to the right.

Numeric Key Pad

These keys are Located at the right hand side of the keyboard. The numeric mode is activated when the numlock key which is a toggle switch is pressed 

Delete Key

Its function is deleting character from the left of the cursor to the right.

Page Up And Page Down Keys

Page up key moves the screen up by one page while page down moves the screen down by one page.

Home And End Keys

Home keys move the cursor to the up left position of the screen while end key moves the cursor to the end of the line. 

  • Pointing Devices

Pointing Device, in computer science, an input device used to control an on-screen cursor for such actions as “pressing” on-screen buttons in dialog boxes, choosing menu items, and selecting ranges of cells in spreadsheets or groups of words in a document. A pointing device is also often used to create drawings or graphical shapes. The most common pointing device is the mouse, which was popularized by its central role in the design of the Apple Macintosh. Other pointing devices include the graphics tablet, the stylus, the light pen, the joystick, the puck, and the trackball. 

a. Mouse: It isa common pointing device, popularized by its inclusion as standard equipment with the Apple Macintosh. With the rise in popularity of graphical user interfaces (Graphical User Interface) in MS-DOS; UNIX, and OS/2, use of mice is growing throughout the personal computer and workstation worlds. The basic features of a mouse are a casing with a flat bottom, designed to be gripped by one hand; one or more buttons on the top; a multidirectional detection device (usually a ball) on the bottom; and a cable connecting the mouse to the computer. See the illustration. By moving the mouse on a surface (such as a desk), the user typically controls an on-screen cursor. A mouse is a relative pointing device because there are no defined limits to the mouse’s movement and because its placement on a surface does not map directly to a specific screen location. To select items or choose commands on the screen, the user presses one of the mouse’s buttons, producing a “mouse click.”See also bus mouse; Mechanical Mouse; Optical Mouse; Opt mechanical Mouse; Serial Mouse; Trackball.

An Optical Mouse 

b.Trackball:This is a popular pointing device that can be roughly described as a mouse on its back. A trackball consists of a ball resting on two rollers at right angles to each other, which translate the ball’s motion into vertical and horizontal movement on the screen. A trackball also typically has one or more buttons to initiate other actions. The only functional difference between a mechanical mouse and a trackball is in how the ball is moved: With a mouse, the ball is rolled by moving the entire unit over a desktop or other surface; with a trackball, the housing is stationary, and the ball is rolled with the hand. A trackball is useful for fine work because the user can exert fingertip control; a mouse is better for bold moves, such as those used in navigating within a graphical user interface. Another major advantage of a trackball is that it takes little desktop surface.

A Track Ball Mouse

C. Touchpad: This is a small, flat, rectangular pointing device that is sensitive to pressure and motion. To move the pointer using a touchpad, you slide your fingertip across the surface of the pad. Some touchpad’s have one or more buttons around the edge of the pad that work like a mouse buttons: on others, you tap the pad’s surface to stimulate mouse operations such as clicking. These are found more often on laptop computers.

  1. Joystick: Joystick is a popular pointing device, used mostly for playing computer games but used for other tasks as well. A joystick usually has a square or rectangular plastic base to which is attached a vertical stem. Control buttons are located on the base and sometimes on top of the stem. The stem can be moved Omni-directionally to control the movement of an object on the screen. The buttons activate various software features, generally producing on-screen events. A joystick is usually a relative pointing device, moving an object on the screen when the stem is moved from the center and stopping the movement when the stem is released. In industrial control applications, the joystick can also be an absolute pointing device, with each position of the stem mapped to a specific on-screen location. A sample image is shown below:

 Two Types Of Joysticks

d. Touch Screen: Touch Screen is a computer screen designed or modified to recognize the location of a touch on its surface. By touching the screen, the user can make a selection or move a cursor. The simplest type of touch screen is made up of a grid of sensing lines, which determine the location of a touch by matching vertical and horizontal contacts. Another, more accurate, type uses an electrically charged surface and sensors around the outer edges of the screen to detect the amount of electrical disruption and pinpoint exactly where contact has been made. A third type embeds infrared light-emitting diodes (LEDs) and sensors around the outer edges of the screen. These LEDs and sensors create an invisible infrared grid, which the user’s finger interrupts, in front of the screen. Infrared touch screens are often used in “dirty” environments where contaminants could interfere with the operation of other types of touch screens.

The touch screen’s popularity with personal-computer users has been limited because users must hold their hands in midair to point at the screen, which is prohibitively tiring over extended periods. Also, touch screens do not offer high resolution—the user is not able to touch only a specific point on the screen. Touch screens are, however, immensely popular in applications such as information kiosks and automatic teller machines because they offer pointing control without requiring any movable hardware and because touching the screen is intuitive.

e. Pen Input: Many input devices use an electronic pen instead of a keyboard or mouse for input. Some of these devices require you to point to onscreen objects with the pen: others allow you to input data using drawings, handwriting, and other symbols that are written with the pen on a surface.

f. Light Pen: Computer engineers have developed an input device that resembles a pen, but uses light. This designer modifies a technical drawing on a computer screen by inputting graphics information with the light pen.

A Light Pen

g. Graphics Tablet:Graphics Tablet, in computer science, also called a digitizing tablet. A flat plastic rectangle with subsurface electronics, used in conjunction with a pointing device in many engineering and design applications as well as in illustration work. When the pointing device is moved on the surface of the tablet, the location of the device is translated to a specific on-screen cursor position. The pointing device used with a graphics tablet is usually a pen (also called a stylus) or a puck. A sample image is shown below:

Examples of Graphic Tablet

  • Scanners and Reading Devices:

Some devices make the input process more efficient by eliminating the manual entry of data. Instead of a person entering data from a keyboard or pointing device, these devices capture data from a source document, which is the original form of the data.

Devices that capture data directly from source documents include optical scanners, optical mark recognition devices, bar code scanners, and magnetic-ink character recognition readers. Examples of source documents used with these devices include advertisements, photographs, brochures, inventory tags or checks.

a. Optical Scanner:This isa computer input device that uses light-sensing equipment to scan paper or another medium, translating the pattern of light and dark (or color) into a digital signal that can be manipulated by either optical character recognition software or graphics software. A frequently encountered type of scanner is “flatbed,” meaning that the scanning device moves across or reads across a stationary document. On a flatbed scanner such as the common office copier, such objects are placed face down on a flat piece of glass and scanned by a mechanism that passes under them. Another type of flatbed scanner uses a scanning element placed in a stationary housing above the document.

Other scanners work by pulling in sheets of paper, which are scanned as they pass over a stationary scanning mechanism, as in the common office fax machine. Some specialized scanners work with a standard video camera, translating the video signal into a digital signal for processing by computer software.

A very popular type of scanner is the hand-held scanner, so called because the user holds the scanner in his or her hand and moves it over the document to be scanned. Hand-held scanners have the advantage of relatively low cost; however, they are somewhat limited by their inability to scan areas more than a few inches wide. A sample image is shown below:

An Optical Scanner

b. Optional Character Recognition Reader: this a device for entering material into a computer by digitizing the image of a printed page, identifying the characters, and storing them as machine code for further processing. Initially such devices could recognize only a specially designed typeface, but modern readers can recognize a wide variety of typefaces. 

c. Bar Code Scanners: They use laser beams to read bar codes. A bar code is an identification code that consists of a set of vertical lines and spaces of different widths. The bar code, which represents some data that identifies the item, is printed on a product’s package or on a label that is affixed to a product so it can be read by a bar code scanner. The bar code scanner uses light patterns for the bar code lines to identify the item.

  • Digital Camera:

A digital camera allows you to take pictures and store the photographed images digitally instead of on traditional film. With some digital cameras, you can download or transfer a copy of, the stored pictures to your computer by connecting a cable between the digital camera and your computer and using special software included with the camera. With other digital cameras, the pictures are stored directly on storage media such as floppy disk, PC Card, or flash card. You then copy the pictures to your computer by inserting the floppy disk into a disk drive or the card into the card slot reader. Once the pictures are on your computer, they can be edited with photo-editing software, printed, faxed, sent via electronic mail, included in another document, or posted to a Website for everyone to see.

  • Audio And Video input:

a. Audio Input: This is the process of entering or recording music, speech, or sound effects. To record high quality sounds, your personal computer must have a sound card. Sound is entered via a device such as a microphone, tape player, or audio CD player, each of which plugs into a port on the sound card.

b. Speech Recognition: In computer science, the ability of a computer to understand the spoken word for the purpose of receiving commands and data input from the speaker. Some systems have been developed that can recognize limited vocabularies as spoken by specific individuals, but developing a system that deals with a variety of speech patterns and accents, as well as with the various ways in which a request or a statement can be made, has so far proved a daunting task for systems designers.

Designers of speech recognition systems have pursued three approaches. One enables computers to recognize a small number of words spoken by a broad range of people. This method has proven to be fairly accurate. The second method enables the recognition of a larger number of words spoken by one individual. This method is also fairly reliable provided the speaker’s speech patterns are consistent. The third method enables computers to learn a speaker’s speech patterns and to apply the patterns over a broad range of words. Although this last method provides the most promise for full speech-to-text conversion, it is the least accurate of the three.

c.Video Input:Video input or video capture is the process of entering a full-motion recording into a computer and storing the video on a hard disk or some other medium. To capture video, you plug a video camera, VCR, or other video device into a video capture card, which is an expansion card that converts the analog video signal into a digital signal that a computer can understand. Once the video device is connected to the video capture card, you can begin recording. After you save the video on a hard disk, you can play it or edit it using video-editing software.

d.Videoconferencing: A videoconference is a meeting between two or more geographically separated individuals who use a network or the Internet to transmit audio and video data. To participate in a videoconference, you must have a microphone, speakers, and a video camera mounted on your computer. As you speak, members of the meeting hear your voice on their speakers. Any image in front of the video camera, such as a person’s face, displays in a window on each participant’s screen.

Another window on the screen that displays notes and drawings simultaneously on all the participants’ screens, called a whiteboard, provides multiple users with an area on which they can write or draw. As the costs of videoconferencing hardware and software continue to decrease, more people and companies are taking advantage of this cost-effective way to conduct business meetings, corporate training, and educational classes.

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