The input output devices including auxiliary memory or backup memory devices are called peripheral devices or computer peripheral. They are called peripheral devices because they are at the periphery of the computer system. These devices are complete units in themselves. Most of the peripheral devices work under the control of a central processor ( in very few systems they work autonomously ). In the following sections, the peripheral devices are described in detail.
Card Reader :
A piece of thin card board which can be punched with holes in order to convert information to a computer is termed as punched card. The punched card is one of the I/O (input / output) medium. It can be used to provide data input to the computer, to receive output from the computer and provide secondary offline storage of data.
The card is divided into 80 vertical columns and 12 horizontal rows: Each column can record one character of information. The character may be a digit or a letter, or a special character.
The data is recorded in a punched card by a key punch or card punch machine. When a key is pressed, the correct combination of holes is produced in the card corresponding to the key pressed. Key punching is similar to typing with a type writer.
A device that can transcribe punched hole data from punched cards into electrical impulses for input into computer memory is called a card reader. Once the data are punched into the cards, they are fed into the central processor by means of a card reader. Cards are placed into a read hopper. After giving the command those cards are moved through the card feed unit past the card reading stations. There are two card reading stations. Those card reading stations detect (sense) presence or absence of holes in each card column and converts such information into electric pulses. The electric pulses are fed to the computer. The card reader can find the accuracy of such reading operation by comparing the electric pulses from two reading stations When cards have been read, they are fed into the stacker hopper. The card reading speed varies from 100 to 2000 cards / min.
Card Reader :
A piece of thin card board which can be punched with holes in order to convert information to a computer is termed as punched card. The punched card is one of the I/O (input / output) medium. It can be used to provide data input to the computer, to receive output from the computer and provide secondary offline storage of data.
The card is divided into 80 vertical columns and 12 horizontal rows: Each column can record one character of information. The character may be a digit or a letter, or a special character.
The data is recorded in a punched card by a key punch or card punch machine. When a key is pressed, the correct combination of holes is produced in the card corresponding to the key pressed. Key punching is similar to typing with a type writer.
A device that can transcribe punched hole data from punched cards into electrical impulses for input into computer memory is called a card reader. Once the data are punched into the cards, they are fed into the central processor by means of a card reader. Cards are placed into a read hopper. After giving the command those cards are moved through the card feed unit past the card reading stations. There are two card reading stations. Those card reading stations detect (sense) presence or absence of holes in each card column and converts such information into electric pulses. The electric pulses are fed to the computer. The card reader can find the accuracy of such reading operation by comparing the electric pulses from two reading stations When cards have been read, they are fed into the stacker hopper. The card reading speed varies from 100 to 2000 cards / min.
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