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Input Devices
O level Computer Science (2210)
Prepared By: Engr. Fahad Khan
An input device is a piece of hardware that is used to enter data into a computer. There are many different kinds of input devices. They are divided into two categories (1) Manual input devices (devices that need human involvement to input data) (2) Automatic input devices (devices that do not need human involvement to input data)
Manual Input Devices are:
(i) Keyboard (ii) Pointing Devices (iii) Scanner (iv) Digital Camera (v) Microphone (vi) Musical Keyboard (vii) Remote Control In the first section, we will discuss manual input devices while in the next section we will discuss automatic input devices or automatic data capture devices.
Keyboard
The keyboard is the most common and widely used input device.
It is made up of buttons called 'keys'. The keys are arranged into sections: Alphabet keys Function or F keys (F1, F2, F3) Numeric keys (one set above the alphabet keys and a numeric keypad on the right) Arrow keys Command keys (insert, delete, home, end, page up/down)
Most keyboards are called 'QWERTY' keyboards. This name comes from the first six letters on the top row of the alphabet keys. Using a keyboard for too long can lead to health problems such as repetitive strain injury (RSI).
To try to overcome this, different styles of keyboard have been developed, for example, the ergonomic keyboard. They are supposed to put your hands into a much more natural position than a traditional keyboard.
Concept keyboard A concept keyboard is a flat board that contains a grid of buttons. Each button can be programmed to do whatever you want. An overlay sheet with pictures or symbols is placed on the grid so that the user can tell what pressing on different areas will do.
Concept keyboards are particularly useful for people who would find using an ordinary keyboard difficult. It is also very handy in locations where an ordinary keyboard might be damaged e.g. by spillage or dust.
Concept keyboards are excellent where there is a limited set of things to select and it needs to be done fast e.g. fast food store, pub, skating and other recreation events.
Touchpad is a pointing device found on most laptops and used instead of a mouse since it takes up less space. The user moves a finger across the touch pad and this movement data is sent to the laptop. Usually used to control the pointer in a GUI.
This pointing device is not moved about like a mouse, instead it has a large ball that the user spins. Data about which direction the ball is spun is passed to the computer. Tracker balls are often used by people with limited movement (disabled).
Joysticks used to be popular with gamers but have slowly been replaced by other types of game controller. Joysticks can also be used for controlling machines such as cranes, trucks and powered wheelchairs.
A touch screen is the only device which works as both an input and an output device. You view the options available to you on the screen (output) and you then use your finger to touch the option that you have chosen (input).
Touch screens are easy to use and are often found in public places such as cashpoints at banks, ticket collection terminals at theatres or airports, information centers at museums.
A light pen is a device used as a pointing device or to ‘write ’ on the screen of a computer. It is connected with computer system through a cord which makes it awkward to be used. Light pens are rarely used today since graphics tablets and high-quality touch screens provide similar functionality.
Scanners
Scanners can be used to convert images or text on paper into a digital format that can be used by the computer. A scanner works by shining a beam of light onto the surface of the object that you are scanning. This light is then reflected back onto a sensor that detects the colour of the light. This is then used to build up the digital image.
Digital Camera A device that captures digital photographs. Most digital cameras do not directly input data into a computer - they store photographs on memory cards. The photographs can later be transferred to a computer.
A modern digital camera can capture 10 Megapixels or more per photograph - that’s 10,000, coloured dots (pixels) in every photo.
A webcam is short for 'web camera'. A webcam is an input device because it captures a video image of the scene in front of it. It is either built in to the computer (e.g. laptop) or it is connected through an USB cable. It is used in video chatting (video calling) over the Internet and sometimes used for security purposes as well.
Microphone A microphone can be used to input sound. The sound is detected by the microphone and an electrical signal is transmitted to the computer. Special hardware is used to convert this analogue data into digital data so it can be stored and manipulated.
In the last few years a number of voice recognition systems have been developed. These packages let the user dictate the text into a computer and then convert the speech to text. Dictating like this can be much quicker than typing but the software isn't perfect and it can interpret a word incorrectly.
- It is quicker to extract text from a document and to use it via word processor.
- It is useful for people with visual impairments because after extracting text from document, a text-to-speech software can be used to read it aloud.
Disadvantage:
- The text recognized by OCR software is not always accurate.
Optical Mark Reading (OMR) software is used to detect the presence of marks (shaded regions) in certain positions on a paper form. Unlike OCR, it cannot detect the characters. OCR software is used to extract marked answers in multiple-choice questions, survey results, votes in elections etc.
Advantage:
- It is extremely fast and accurate because shaded regions are simple to detect.
Disadvantages:
- Paper forms can be read accurately only if they are lined up properly.
- The dirty marks on the paper can be read by OMR as well which leads to wrong results.
MICR (Magnetic Ink Character Recognition) MICR software scans documents for numerals and symbols printed in magnetic ink. The use of magnetic ink makes documents harder to copy. MICR is mostly used by bank cheque-processing systems for input of printed items on the bottom of each cheque.
Advantages:
- It is highly accurate to recognize numerals and symbols even if they are overprinted by visible marks.
Disadvantages:
- MICR readers are expensive and only detects magnetic ink characters.
Magnetic Stripe Reader Magnetic stripe readers are used to read the magnetic strips usually printed on the back of debit cards, credit cards, library cards etc. The magnetic stripe has 3 independent parts that can store different types of information. It can only store a small amount of data but this is sufficient for many purposes.
Advantages:
- Putting a magnetic stripe on the cards is not expensive.
Disadvantages:
- It is easy to write fresh data on the magnetic stripe so someone can easily alter the data on the card with a magnetic stripe writer.
- Someone can easily clone a card by entering the duplicate information on magnetic stripe.
Smart Card Reader
A smart card is a plastic card with a built-in microprocessor, used typically to perform financial transactions. It resembles a credit card in size and shape. While making a payment, a smart card is inserted in the smart card reader. The user enters a four digit Personal Identification Number (PIN) to access the data stored in card. The smart reader communicates with the built-in processor of card to match the PIN with already stored PIN and also authenticates that card is not expired.
Advantage:
- It is not easy to clone or to copy a smart card.
Disadvantage:
- If the PIN is shared or seen then someone can misuse it easily by stealing the card.
Barcode Reader A barcode is a set of parallel lines in contrasting colours usually black lines on a white background. Barcodes are used to identify items of merchandise, resources, membership cards or documents. A barcode may represent numeric digits or alphanumeric characters. A barcode only tells about the manufacturer and product only. A barcode reader is usually used at Point-of-Sale (POS).
A barcode reader is a combination of scanner hardware and software. The scanner captures the image of barcode while software decodes the barcode in captured image.
At POS , a barcode reader consists of a scanner wand or a LASER scanner fixed at the operator’s computer. In these dedicated scanners a suitable processor and a decoding software are built-in the scanner. It sends signals of decoded barcode to the computer for further processing.
Advantages:
- Codes can be entered much faster than keyboard.
- Codes can be entered more accurately than a person.
Disadvantage:
- Barcode is difficult to read or may be misread by barcode reader if it is obscured.
RFID Tag Reader A Radio Frequency Identification (RFID) tag reader reads an ID code from a small tag using short range wireless signals.
The ID code is stored in RFID tag. An RFID tag consists of Read Only Memory (ROM) to store code, a small processor and an antenna to transmit and receive signals. The size of RFID tag is very samll in millimeters usually.
Applications:
- Used in inventory management systems.
- Used for parking and toll charges
Types of Sensors
- Temperature Sensor
- Pressure Sensor
- Light Sensor
- Infrared Sensor
- Humidity Sensor
- Gas Sensor
Temperature Sensor
A temperature sensor detects the temperature from its surroundings and produces a signal that is sent to the computer for processing.
Uses/Applications:
- Used in electronic thermometers
- Used in heat systems to control the temperature automatically
Pressure Sensor
When a pressure sensor is exposed to pressure then it generates signals that are sent to the computer for processing purpose.
Uses/Applications
- It is used in automatic blood pressure monitoring device.
- Used to control the pressure of gas or liquids in a chemical reaction vessel.
Light Sensor A light sensor produces a signal that depends on the intensity of light falling on it. This signal is sent to the computer for processing.
Uses/Applications:
- Used in cars to control the headlights automatically.
- Used in streetlights to turn on/off automatically
Infrared Sensor
An infrared sensor produces a signal that depends on the level of invisible IR radiation falling on it. All objects (unless they are extremely cold) emit significant IR radiation.
Applications:
- Used in railway safety system
- Heating & night visions
- Flame detection
Humidity Sensor A humidity/moisture sensor produces a signal that depends on the amount of water vapors in the atmosphere.
Applications:
- Used in controlling automated irrigation systems
- Used in controlling a heating, ventilating and air conditioning (HVAC) system.
- Used to maintain sufficient humidity in a greenhouse.
- Can be used to measure humidity for weather forecasting.
Gas Sensor
A gas sensor produces a signal depending on the concentration of a particular gas or vapors.
Applications:
- Use for an inflammable gas to monitor the atmosphere.
- Used in process control of chemical industry.
- Environmental Monitoring of air pollution.
Question 4: (May/June 2013, P11, Q5)
Question 05: (May/June 2014, P11, Q10)
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Question 07: (May/June 2014, P12, Q12)
Question 08: (May/June 2014, P12, Q6)
