Input and Output Devices Of Computer | A Complete Detailed Guide. Very Useful For All Competitive Exams
Input Devices
Data and instructions are entered into a computer through input devices and input device converters input data and instructions into a suitable binary form, which is stored in the man memory of a computer.
The Different Types of Input Devices of a Computer are explained below.
A. Keyboard
Computer keyboard is an electromechanical component. It creates special standardized electronic codes when a key is pressed. The codes are transmitted along the cable that connects the keyboard to the computer system unit or terminal, where the incoming code is analyzed and converted into the appropriate computer usable code. Keyboards come in a variety of sizes and shapes having a number of features in common:
1. Standard Type Writer keys
- The keyboard has typewriter like keys.
- These keys are 0-9 and character keys like A-Z and special symbols like ~, !, @ etc.
- These keys are called QWERTY keys.
2. Function keys
- Keys Fl to F12, on the top of the keyboard are called function keys.
- These are programmable keys.
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3. Special purpose keys
- Backspace Key
- Backspace key erases one character to the left of the cursor.
- Enter Key
- Enter key is used to start a new line.
- Enter key also terminates a command. Then the command is executed.
- Esc Key
- Esc Key is used to cancel a command
- Caps Lock Key
- Caps Lock key is a toggle key.
- If Caps Lock key is ON (the Caps Lock light at upper right side of keyboard is On) all typed characters will be in upper case (capital).
- Pressing the key again will put Caps Lock OFF (the Caps Lock light will be off). Now all the typed characters will be in lower case (small).
- Shift Key
- Any character key, pressed along with Shift key, changes its case. For E.g. if caps lock is on, and you want a character in lower case, press Shift key and that character together. Same in the case you want Upper case character when caps lock is off.
- To print symbols, printed on number keys, press that key with Shift key.
- To use upper symbol in the keys having two symbols, press that key with Shift key.
- Tab Key
- Tab key lets your cursor jump predefined number of spaces mostly 5 spaces.
- Ins Key
- Ins key is a toggle key.
- Pressing Ins Key toggles between Insert mode and Overstrike mode.
- When in Insert mode, you can add a character anywhere in a word. The characters at the position of insertion shift to right to make place for new character. In Overstrike mode, each new character overwrites the already written character at that position.
- Delete Key
- Delete key is used to delete one character above cursor.
4. Cursor movement keys
These are four keys.
These keys are used to move cursor left, right, up or down.
Other keys Home and End keys are used to go to beginning and end of line respectively.
5. Numeric keys
Numeric keypad is on the right side of keyboard.
To use these keys press Num Lock (first key on the numeric keypad) to swith on num lock the light will be on).
These keys make entry of numeric values faster.
Mouse
The mouse is an input device that is much in use nowadays in graphics as well as when working with a GUI (Graphical User Interface). It slides on a rubber ball and has two or more buttons on the top. When a mouse is slid across a flat surface, the screen cursor also moves in the direction of the movement of the mouse. With a click of the button, the system can be notified of the selected position.
Joystick
A Joystick is a pointing device used to move the cursor position on the screen. It has a spherical ball at its lower end as well as at its upper end. The lower spherical ball moves in a socket. The joystick can be moved right or left, forward or backward. It is mostly used in Video Games.
Scanners
These are basically input devices that are capable of recognizing marks or characters. They are used for direct entry of data into the computer. Reduction in human intervention improves data accuracy. Since scanners are direct data entry devices, so they demand high quality documents.
MICR
Magnetic ink character recognition devices were developed to assist the banking industry. It is used in the processing of cheques.
The most commonly used character set by MICR devices is known as E13B font that consists of numerals 0-9, and 4 special characters.
These help in sorting of cheques/drafts based on the code printed on the cheque using the E13B font.
Processing is speeded up using MICR but the main limitation is that only 10 digits and 4 characters are used.
OMR (Optical Mark Reader)
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Optical Mark Readers are scanners used for recognizing a pre-specified type of mark made by pen or pencil on specially designed sheets.
These scanners are mostly used in evaluating objective type examinations.
Checking presence or absence of mark at definite position does the grading.
Bar Code Reader
Data coded is in the form of light and dark lines or bars are known as bar codes. Particularly the retail trade for labeling goods uses bar codes. Bar code reader is a device used for reading bar coded data.
Bar code reading is performed by a laser-beam scanner, which is linked to a computer.
Desk Scanning
During the scanning process, the scanner applies a light source to your image.
The light is reflected back from the image into the scanner optics where the varying levels of light are interpreted.
Your image is then reconstructed digitally and displayed on your screen.
Unlike a camera image, scanning software lets you alter the information from the image stored in the computer and used in any application.
Web cam
A webcam is a video capture device connected to a computer or computer network.
Web cam is widely used for video telephony, permitting a computer to act as a video conferencing station.
Webcams are low cost form of videotelephony.
Output Devices
Results of processing are shown through output devices
The Different Types of Input Devices of a Computer are explained below.
Monitors
This is the most popular I-O device used nowadays for interactive processing.
A keyboard is used to enter data into a processor and a video display unit called Monitor- is used to display the keyed data and to receive processed information and messages from the computer.
Printers
Printers are primary output devices used to prepare permanent documents for human use. Printers, on the basis of technology used in them, can be categorized as:
Impact Printers
These operate like a typewriter, pressing a typeface against paper and inked ribbon e.g. daisy- wheel printer, dot-matrix printer.
DMP (Dot Matrix Printer)
These are serial printers, i.e., they print one character at a time.
Each character is printed as a pattern of dots.
The print head comprises of a matrix of tiny needles typically a 9 rows 7 columns matrix, which hammers out characters in the form of patterns of tiny dots.
Non-Impact Printers
These use thermal, electrostatic, chemical, and inkjet technologies.
Ink Jet printer
The ink jet printer ejects a steady stream of ink drop towards the printed page. The drops are selectively discarded by electrostatic attraction to leave only those that are needed to form the desired symbol. Those that are not needed are captured in a tiny gutter & filtered to remove impurities. They are then recycled through the drop- generating mechanism.
Laser Printer Technology
Laser Printer is much less mechanical than impact printing
A laser beam is directed across the surface of a light-sensitive drum and fared as needed to record an image in the form of a pattern of tiny dots.
The image is then transferred to the paper, a page at a time, in the same fashion as a copy machine, using a special toner.
The major advantages of laser printers are:
1. Very high speed.
2. Low noise level.
3. Low maintenance requirements.
4. Very high image quality.
5. Excellent graphics capabilities.
6. A variety of type sizes and style.
7. On large, high-speed laser printers, forms can be printed at the same time data is recorded in them.
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