• COMPUTER HARDWARE
A computer system consists of hardware and software. The physical components of a computer that we can see, touch and feel are called hardware. Computer hardware consists of input/output devices, storage devices, central processing unit (CPU) and the electronic circuitry that links these devices for Communication between them.
• INPUT DEVICES
The input devices are used to communicate with the computer. They consist of devices that accept data and convert it into machine readable form. These devices are often referred to as peripherals because they are physically separated from the system unit. Some input devices are keyboard, mouse, joystick, microphone and image scanners.
Keyboard is the primary input device for the input of data to a Computer, though voice input devices may ultimately supersede it. It operates by Converting key presses to electronic signals in digital form. Keyboard has the standard character keys together with numeric keys and special keys.
• Pointing Devices
Pointing devices are used to Control the movement of the pointer (cursor) to select items on a screen or open Computer programs or files. Commonly used pointing devices are mouse, trackball, joystick, touch Screen, light pen and touch pad.
Mouse is a pointing device. As we move the mouse over the surface of desk, the movements of the ball are detected by the internal mechanism. At the front of the mouse’s casing are two or three buttons. These buttons are used to perform tasks, such as picking options displayed on the screen. Optical mouse is becoming very popular and it is replacing the mechanical mouse. An optical mouse uses a light-emitting diode and photo-diodes to detect movement relative to the underlying surface, rather than internal moving parts (mouse ball and rollers) as in mechanical mouse.
Mouse is an essential part of the hardware on almost all the microcomputers running Windows and other application software.
Trackball remains stationary on the surface. The ball, at the top, is rolled with fingers. It has buttons that are used to perform operations similar to those performed by a mouse.
Joystick is commonly used for playing computer games. It is fixed On the table and it has a Stick in the Center that can be tilted in any direction. The stick is held by hand and when it is tilted in any direction, the movement is translated into the movement of an object on the screen. The buttons are used to perform actions such as firing guns and lasers.
• Touch Screen
A touch screen is a computer display screen. It is an input as well as output device. The screen is sensitive to pressure. User interacts with the computer by touching pictures or Words on the screen. Instead of using a pointing device user can use finger to point directly to objects on the screen. Touch screens are generally attached to computers but they are also popular in other devices such as mobile phones, satellite navigators and Personal Digital Assistants (PDAs).
• Light Pen
It looks like a pen with a photocell at its tip. It is used to point to an objector draw on the screen. It gives more accuracy than pointing with Our finger on the touch screen. It is mainly used in engineering for designing purpose.
Touchpad is used in laptop computers. It is a pointing device that can sense the movement and position of finger on the pad. They are Commonly used as an alternate to computer mouse in a laptop Computer. There are two buttons located above or below the pad and their function is the same as the buttons on the mouse.
Microphone is used to convert the spoken words to digital signals for computer input. It converts audio signals to electrical waves and these are converted by electronic circuitry in the computer to digital form.
• Digital Camera
It is a camera that Captures pictures and stores them in digital form. Pictures taken by a digital camera can be downloaded to a computer for viewing and editing.
Digital cameras have a LCD for viewing both images in the viewfinder and those in the camera’s memory. It is an input as well as output device.
Scanner is an optical input device that optically scans printed or handwritten text and images and stores them in Computer memory in digital form. Nowadays, Scanners are widely used to get drawings, diagrams and photographs into Computer systems for incorporation into documents and books which are made up electronically prior to printing. There are different types of scanners like hand-held scanner, flatbed Scanner and barcode reader.
• Hand-held Scanner
To scan an image, the hand-held scanner is dragged Over the image to be scanned. The hand-held Scanner should be moved carefully with uniform speed because uneven scanning rate would produce distorted image. Hand-held scanners are very useful for scanning articles from magazine, newspapers and books.
• Flatbed Scanner
In a flatbed scanner, the image to be scanned is placed face down on the glass and a cover is lowered over it to exclude light. The camera moves across glass pane, reading the entire area.
• Barcode Reader
Barcode reader is also a type of scanner which is used to scan barcode, also called UPC (Universal Product Code), available on various products. These barcodes Contain information about the product like name of the product, Company, manufacturing date, expiry date, etc. This information is provided to the computer for further processing like generating bills at check outs in shopping malls. Prices are normally not included in barcodes because prices are not constant and may change frequently.
• Magnetic Stripe Cards
Magnetic stripe card has a magnetic stripe which is used to store data in the form of tiny magnetized and non-magnetized particles of magnetic material. The information on the card is read by Swiping the Card past a magnetic reading head. Examples of these cards include credit cards, ATM cards, VISA and MasterCard, driver’s license and membership cards.
• OUTPUT DEVICES OF COMPUTER
Output devices consist of Computer components such as monitor, printer, speaker and plotter that transfer information from computer memory to the outside world. They display or print text, graphics or pictures. The output generated on paper by an output device such as printer or plotter is called Hardcopy output. The output in the form of data or information stored on a storage device or displayed on a monitor is called Softcopy output.A monitor, sometimes called a VDU (Visual display unit), is an electronic output device for Computers. It displays the results of the user activities. The output produced by monitors is called softcopy output. There are different types and sizes of monitors, each can be distinguished on the basis of the following features:
• Size: The size of the monitor is measured diagonally. Standard size of monitor is from 15 to 22 inches.
• Color: The monitor can be either black and White or Color.
• Pixel: Pixel is a small/tiny dot on the monitor which forms the image. • Resolution: The number of pixels (or dots) per square inch is Called the resolution of the monitor.
• Dot Pitch: The distance between the pixels on the monitor is called dot pitch. The lesser the dot pitch more will be resolution of the monitor.
CRT (cathode ray tube), LCD (Liquid Crystal Display) and LED (Light emitting diodes) are the Common types of monitors.
CRT monitors are similar to the standard television sets because they contain Cathode Ray Tube. The Cathode Ray Tube (CRT) is a vacuum tube containing an electron gun and a phosphors Coated screen. The electron gun, fires a beam of electrons which falls repeatedly on the phosphors coated screen and it glows for a fraction of a second. In color CRT monitors there are three electron guns while the phosphors atoms are in three different colors i.e. Red, Green, Blue (RGB). Other colors are produced by the combinations of these three Colors.
• Liquid Crystal display (LCD), Monitors
Liquid Crystal Display (LCD) is a thin and light weight monitor. It contains a substance called liquid Crystal between two sheets. The molecules of this substance are lined up in such a way that the light behind the screen is blocked or allowed to create an image on the screen. LCDs provide a sharper image than CRT monitors and emit less radiation. They are used in a wide range of applications, including Computer monitors, televisions, and clocks. They are usually more Compact, lightweight, portable, less expensive, more reliable, and easier on the eyes than CRT monitors.
• Light emitting diodes (LED) Monitors
LED monitor is a light-weight flat panel display unit, which uses LEDs (light-emitting diodes) as pixels for display. In contrast to LCDs these monitors produce bright images and emit less radiations. LEDs run at lower temperatures and Consume less power as Compare to LCDS. Their lifespan is also longer than other types of monitors. The only drawback is that these monitors are expensive than other types of monitors.
Printers are used to produce hardcopy of output. In the past, printers were connected to the computer through parallel port but now they are connected through USB port.
Printers vary in their capabilities based on the following characteristics.
• The quality of output
• The ability to print graphics
• The printing speed.
There are two main Categories of printers.
• Impact printers
• Non-impact printers
• Impact Printers
Impact printers are those printers which work like typewriters. Impact printers use electromechanical mechanism, which causes the character shape to strike against the paper and leave an image of character on the paper. Examples of impact printers are dot matrix and chain printers. Their print quality is low and they produce noise.
Dot matrix printers have 9 or 24 pins arranged in a matrix to print shapes of characters.
• Chain printer
Chain printer is very old type of line printer. It contains characters in a chain. The chain moves rapidly by two geared pulleys while printing.
• Non-impact Printers
Non-impact printers produce a printed image without striking the paper. The printing quality and speed of these printers is better than impact printers. These printers produce very little noise while printing. Commonly used non impact printers are inkjet and laser printers. Inkjet printers are character printers. They form characters and all kinds of images by spraying small drops of ink on the paper. Inkjet printers are cheap, quiet in operations and can print in multicolour but the printing quality and speed is slower than laser printers.
• Laser printers
Laser printers are page printers, meaning that they print an entire page at a time. Their printing technology is very similar to photocopiers. They are very fast and silent in operation. The print quality of laser printer is very high and they can print graphics in multicolour.
Plotters are output device used to produce large size hardcopy output. Plotters are used for a variety of applications, which include drawing graphs, making maps, plotting civil engineering drawings/machine components and producing large size panaflexes. Plotters are of two types i.e. flatbed and drum.
• Flatbed Potter
Flatbed plotter plots on paper that is spread and fixed over a rectangular flatbed. Pens of different colours are mounted in the pen holding mechanism that moves on the surface to draw the image.
• Drum Plotter
In drum plotter, paper/sheet is fed from one side and drum of the plotter rotates to move the paper to the other side. These plotters are used to print large size of panaflexes.
Speakers are audio output devices that are attached to the Sound Card on motherboard. Speakers produce softcopy output in the form of voice. Speakers are available in different shapes and sizes.