Input / Output Devices
Some devices fulfill both input and output functions for a computer system. They act as an interface for data going in as well as out and sometimes they do this simultaneously. One such device is the modem.
Modem
The modem is used to connect the computer to the telephone line. The telephone network operates using analogue voice signals, while a computer operates on digital signals. The modem is the bridge between the digital and the analog signals, and therefore provides an interface between computer and telephone systems.
The modem converts on and off digital data into an analogue signal by varying, or modulating, the phase and frequency of an electronic wave. On the receiving end of a phone connection, a modem does just the opposite: it demodulates the analogue signals back into the digital code. These two terms MOdulate and DEModulate give the modem its name.
Showing posts with label Input Devices. Show all posts
Showing posts with label Input Devices. Show all posts
Wednesday, June 10, 2009
Special Input Devices
Special Input Devices
Bar Code Readers
A bar code is a set of parallel lines of varying thickness, which are alternately black and white, which represents a number. The number represented by the bars is also printed above or below the bar code. Bar codes may be read by a hand held scanner, which is passed over the bar codes. The scanner is attached to a computer terminal or a stationary scanner, which scans the bar code as it is passed over it.
When bar codes are used for products in shops the coded number usually contains:
• Country of origin
• Manufacturer
• Item number for the product
We have to note that the price is not included in the bar code. This is because the prices change often. Instead the price is stored in the computer and when the price is needed it can be retrieved. The expiry date is also not included since it too may change.
Bar codes are used in products in supermarkets, books and magazines in libraries, luggage at airports and warehouse stock control systems. Bar code systems are now at an advanced stage and readers are able to read the bar codes at distances of five meters or more. This fact has increased the number of applications.
Magnetic Ink Character Recognition (MICR)
Magnetic ink characters printed using magnetic ink, are the numbers that you see at the bottom of bank cheques. As the document is passed through the reader the ink is magnetized and the characters are recognized by their strength of magnetism.
Most banks use the MICR to encode the following information from the magnetic ink characters at the bottom of the cheques:
• the cheque number
• the branch number of the bank
• the customer's account number
Optical Character Reader (OCR)
The document is first scanned using a scanner. The software used to scan the document would be an Optical character recognizer. Then the document can be saved in ¬a word processor. i.e. As a MS Word document.
An optical character reader recognizes characters from their shape. Text is input using a scanner and special OCR software. OCR involves scanning the image of a page of text with a scanner, and then using special software, it converts the scanned image into standard ASCII code, which recognizes each of the characters separately, so that they may be altered if needed, using a word processor. Scanners often have OCR software included in their price.
Optical Mark Reader (OMR)
Optical mark readers are able to sense marks made in right positions on a special form. These forms include multiple choice answer sheet marking (MCQ papers), questionnaires and enrolment forms which are data capture forms for OMRs.
Voice Recognition
Using a microphone, human speech is coded into a sequence of electrical signals and the computer searches a set of stored patterns for the sound, which has been the input.
Voice recognition is useful where only a few different commands are required and the hands are busy to type or use the mouse. On some advanced jet fighters the pilot has a small display of some of the instruments. Using one of a number of simple pre-stored voice commands this display can be changed. Relatively few words can be recognised and the error rate is high. The system is not suitable for use in noisy places.
Digitizer
Digitizers are rather like electronic tracing paper and, like paper they come in all sizes from a modest A4 size to a very large AO size. A cursor or pointer is used on a graphics tablet to trace over technical drawings put on the screen using a computer- aided-design package such as AutoCAD.
Smart Cards
A smart card is a plastic card, which has its own processor and memory chips. One card can store about 8000 characters. The holder's identification data is stored in the card.
These cards are used in a variety of applications such as:
• Checking authorization for accessing security sites - The user inserts the smart card into a reader when prompted to enter the password. If the password is correct the user will be granted entry to the particular site. (The user is usually asked to reconfirm the password). The processor inside the smart card can be programmed to self-destruct if the wrong password is entered too many times.
• Telephone cards - The card is inserted into a slot found in the telephone box and the relevant amount will be reduced from the value of the card after the call.
• Credit cards - The card conceals the holder's identification data and the credit limit, which are used in supermarkets and leading shops. It holds the details of transactions made by using the card.
Point-of-Sales (POS) Systems
In a typical POS/cash transaction, a cashier passes the bar-coded product over a scanner or hand-held 'wand'. The computer can store the data for stock control and data analysis. The terminal is usually connected to a central computer, which would be the central database, which reads and records details, looks up the price of the product and displays the price on a lighted panel. It also computes the amount due and prints an itemized receipt.
This method of data is beneficial:
• To the customer - It forms the basis for a computerized checkout system. Customers get a quicker and more accurate service, (no time wasted or mistakes made when entering prices) as well as an itemized receipt.
• To the supermarket - The result is that the supermarket management can get instant or continuous stock checks and adjusting orders precisely to the flow of goods, thus improving efficiency. The cost of adding a bar code to a label is tiny and it saves time.
Bar Code Readers
A bar code is a set of parallel lines of varying thickness, which are alternately black and white, which represents a number. The number represented by the bars is also printed above or below the bar code. Bar codes may be read by a hand held scanner, which is passed over the bar codes. The scanner is attached to a computer terminal or a stationary scanner, which scans the bar code as it is passed over it.
When bar codes are used for products in shops the coded number usually contains:
• Country of origin
• Manufacturer
• Item number for the product
We have to note that the price is not included in the bar code. This is because the prices change often. Instead the price is stored in the computer and when the price is needed it can be retrieved. The expiry date is also not included since it too may change.
Bar codes are used in products in supermarkets, books and magazines in libraries, luggage at airports and warehouse stock control systems. Bar code systems are now at an advanced stage and readers are able to read the bar codes at distances of five meters or more. This fact has increased the number of applications.
Magnetic Ink Character Recognition (MICR)
Magnetic ink characters printed using magnetic ink, are the numbers that you see at the bottom of bank cheques. As the document is passed through the reader the ink is magnetized and the characters are recognized by their strength of magnetism.
Most banks use the MICR to encode the following information from the magnetic ink characters at the bottom of the cheques:
• the cheque number
• the branch number of the bank
• the customer's account number
Optical Character Reader (OCR)
The document is first scanned using a scanner. The software used to scan the document would be an Optical character recognizer. Then the document can be saved in ¬a word processor. i.e. As a MS Word document.
An optical character reader recognizes characters from their shape. Text is input using a scanner and special OCR software. OCR involves scanning the image of a page of text with a scanner, and then using special software, it converts the scanned image into standard ASCII code, which recognizes each of the characters separately, so that they may be altered if needed, using a word processor. Scanners often have OCR software included in their price.
Optical Mark Reader (OMR)
Optical mark readers are able to sense marks made in right positions on a special form. These forms include multiple choice answer sheet marking (MCQ papers), questionnaires and enrolment forms which are data capture forms for OMRs.
Voice Recognition
Using a microphone, human speech is coded into a sequence of electrical signals and the computer searches a set of stored patterns for the sound, which has been the input.
Voice recognition is useful where only a few different commands are required and the hands are busy to type or use the mouse. On some advanced jet fighters the pilot has a small display of some of the instruments. Using one of a number of simple pre-stored voice commands this display can be changed. Relatively few words can be recognised and the error rate is high. The system is not suitable for use in noisy places.
Digitizer
Digitizers are rather like electronic tracing paper and, like paper they come in all sizes from a modest A4 size to a very large AO size. A cursor or pointer is used on a graphics tablet to trace over technical drawings put on the screen using a computer- aided-design package such as AutoCAD.
Smart Cards
A smart card is a plastic card, which has its own processor and memory chips. One card can store about 8000 characters. The holder's identification data is stored in the card.
These cards are used in a variety of applications such as:
• Checking authorization for accessing security sites - The user inserts the smart card into a reader when prompted to enter the password. If the password is correct the user will be granted entry to the particular site. (The user is usually asked to reconfirm the password). The processor inside the smart card can be programmed to self-destruct if the wrong password is entered too many times.
• Telephone cards - The card is inserted into a slot found in the telephone box and the relevant amount will be reduced from the value of the card after the call.
• Credit cards - The card conceals the holder's identification data and the credit limit, which are used in supermarkets and leading shops. It holds the details of transactions made by using the card.
Point-of-Sales (POS) Systems
In a typical POS/cash transaction, a cashier passes the bar-coded product over a scanner or hand-held 'wand'. The computer can store the data for stock control and data analysis. The terminal is usually connected to a central computer, which would be the central database, which reads and records details, looks up the price of the product and displays the price on a lighted panel. It also computes the amount due and prints an itemized receipt.
This method of data is beneficial:
• To the customer - It forms the basis for a computerized checkout system. Customers get a quicker and more accurate service, (no time wasted or mistakes made when entering prices) as well as an itemized receipt.
• To the supermarket - The result is that the supermarket management can get instant or continuous stock checks and adjusting orders precisely to the flow of goods, thus improving efficiency. The cost of adding a bar code to a label is tiny and it saves time.
Tuesday, June 9, 2009
Input Devices
Input Devices: The user connection
Most of the data comes in hand written forms that cannot be directly input into the computer. These documents need special data preparation devices that translate the source document into a medium that the computer can read, such as a magnetic disk. Input devices are used to input or capture data into a computer system. The ideal input device would be able to get data into a system as accurately as possible in the least amount of time.
There are wide ranges of input devices used today:
Keyboard
The keyboard of all input devices is the oldest and most familiar. Keyboards are devices that contain their own chips. Basically each key in the keyboard acts as a switch, which is switched on when the key is pressed.
The microprocessor scans the keyboard hundreds of times a second to see if a key has been pressed; if it has, a code that denotes which key has been pressed is sent to the processing unit. The CPU translates this code into an ASCII code (the code that computers use to represent characters on the computer keyboard), which is then used by a computer program.
Mouse
A mouse is an input device that usually has one, two or three buttons, which are used to make selections on the screen. It is a pointing device. A mouse translates its movements on the desktop into digital information; this is fed to the computer, which in turn causes the cursor to move on the screen. The cursor is the blinking line on the screen, which indicates that the computer is ready to type. Underneath the mouse is a rotating ball and as the mouse is moved on the desk, and sensors pick up this movement to move the pointer on the screen. (The pointer helps the user point and click on an icon or menu on the screen).
Trackball
What do you get when you turn a computer mouse upside down? A trackball! The ‘mouse' stays still while the user rotates the ball. Trackballs are often seen on laptop computers because it has the advantage of taking up much less space compared with a conventional mouse. It is a pointing device.
Joystick
A joystick is similar to a trackball. Whenever the stick is moved, the pointer moves in a similar direction on the screen. Joysticks are commonly used for games, but you can also see them being used for scanning purposes in hospitals.
Scanner
Scanners are used to scan text or pictures into a computer's memory. Then the scanned image is manipulated in some way before being printed. There are cheap hand held scanners and or flatbed A4 sized ones. Both black and white and color scanners are available.
Touch Screen
A touch screen is a special kind of screen. This is sensitive to touch. A selection is made from usually a menu present on the screen, which is activated by touching part of it. These screens are ideal for use in banks, restaurants and bars, where customers who are not use to keyboards can obtain information about the services offered.
Light Pen
A light pen is a pen-shaped device held in the hand. The presence or absence of light is detected by it. The pen is used to select a particular point on the screen. The screen is refreshed about every 1/50th of a second by a point of light travelling rapidly across it. The pen detects this point of light and the computer can work out by precise timing where the pen is. Light pens need special software to make them work and are mainly used for design work using CAD packages.
Digital Camera
Digital cameras allow the user to transfer the photographs taken, directly into the computer. Previously, if a photograph had to be input into the computer, it had to first scan using a computer scanner and then viewed on the screen. Digital cameras eliminate the requirement for a scanner. No film or photographic paper is needed. The quality of photographs obtained even from low cost digital cameras is quite good. Digital cameras are very efficient to use especially if you want to take photos and edit them later on the computer.
Sensors
For industrial computer applications, such as process control, the computer is required to interact directly with the plant. Since the computer can only communicate with the outside world by using electrical signals, any devices connected to it must be made compatible using analog to digital converters (ADC) and digital to analog converters (DAC).
Sensors are designed to pick up analogue values of the physical variables and feed them into the computer.
Example:
• temperature
• pressure
• intensity of light
• electrical voltages
• electrical currents
• switch positions
Depending on the values received by the computer, it activates other output devices like motors, valves etc.
Most of the data comes in hand written forms that cannot be directly input into the computer. These documents need special data preparation devices that translate the source document into a medium that the computer can read, such as a magnetic disk. Input devices are used to input or capture data into a computer system. The ideal input device would be able to get data into a system as accurately as possible in the least amount of time.
There are wide ranges of input devices used today:
Keyboard
The keyboard of all input devices is the oldest and most familiar. Keyboards are devices that contain their own chips. Basically each key in the keyboard acts as a switch, which is switched on when the key is pressed.
The microprocessor scans the keyboard hundreds of times a second to see if a key has been pressed; if it has, a code that denotes which key has been pressed is sent to the processing unit. The CPU translates this code into an ASCII code (the code that computers use to represent characters on the computer keyboard), which is then used by a computer program.
Mouse
A mouse is an input device that usually has one, two or three buttons, which are used to make selections on the screen. It is a pointing device. A mouse translates its movements on the desktop into digital information; this is fed to the computer, which in turn causes the cursor to move on the screen. The cursor is the blinking line on the screen, which indicates that the computer is ready to type. Underneath the mouse is a rotating ball and as the mouse is moved on the desk, and sensors pick up this movement to move the pointer on the screen. (The pointer helps the user point and click on an icon or menu on the screen).
Trackball
What do you get when you turn a computer mouse upside down? A trackball! The ‘mouse' stays still while the user rotates the ball. Trackballs are often seen on laptop computers because it has the advantage of taking up much less space compared with a conventional mouse. It is a pointing device.
Joystick
A joystick is similar to a trackball. Whenever the stick is moved, the pointer moves in a similar direction on the screen. Joysticks are commonly used for games, but you can also see them being used for scanning purposes in hospitals.
Scanner
Scanners are used to scan text or pictures into a computer's memory. Then the scanned image is manipulated in some way before being printed. There are cheap hand held scanners and or flatbed A4 sized ones. Both black and white and color scanners are available.
Touch Screen
A touch screen is a special kind of screen. This is sensitive to touch. A selection is made from usually a menu present on the screen, which is activated by touching part of it. These screens are ideal for use in banks, restaurants and bars, where customers who are not use to keyboards can obtain information about the services offered.
Light Pen
A light pen is a pen-shaped device held in the hand. The presence or absence of light is detected by it. The pen is used to select a particular point on the screen. The screen is refreshed about every 1/50th of a second by a point of light travelling rapidly across it. The pen detects this point of light and the computer can work out by precise timing where the pen is. Light pens need special software to make them work and are mainly used for design work using CAD packages.
Digital Camera
Digital cameras allow the user to transfer the photographs taken, directly into the computer. Previously, if a photograph had to be input into the computer, it had to first scan using a computer scanner and then viewed on the screen. Digital cameras eliminate the requirement for a scanner. No film or photographic paper is needed. The quality of photographs obtained even from low cost digital cameras is quite good. Digital cameras are very efficient to use especially if you want to take photos and edit them later on the computer.
Sensors
For industrial computer applications, such as process control, the computer is required to interact directly with the plant. Since the computer can only communicate with the outside world by using electrical signals, any devices connected to it must be made compatible using analog to digital converters (ADC) and digital to analog converters (DAC).
Sensors are designed to pick up analogue values of the physical variables and feed them into the computer.
Example:
• temperature
• pressure
• intensity of light
• electrical voltages
• electrical currents
• switch positions
Depending on the values received by the computer, it activates other output devices like motors, valves etc.
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