Input and Output Devices-4

Still today we have discussed for different types of the computer hardware devices. Form last few days we are talking on input and output devices which is most important part of the computer hardware. The input or output units of a computer system establish the communication between the system and its users. A large number of input and output units are available in the market. A few of them are discussed in this note.

Most recent trend for data input is towards source data automation. The equipments used for source data automation capture data as a by-product of a business activity thereby completely eliminating manual input of data. Some examples are:

1. Magnetic ink character recognition devices are used by the banking industry to read the account numbers on cheques directly and do the necessary processing.
2. Optical mark recognition devices can sense marks on computer readable papers.

This king of device is used by academic and testing institutions to grade aptitude tests where candidates mark the correct alternatives on a special sheet of paper. These answer sheets are then directly read by the optical mark recognition devices and the information sent to a computer for processing.

Input and Output Devices-3

We talked about input or output units of a computer system. Input and output establish the communication between the system and its users. A large number of input and output units are available in the market. A few of them we are discussing here. We talked about hard disk in our previous post. Today we are going to talk about printer.

 

A printer is a peripheral which produces a hard copy of documents stored in electronic form, usually on physical print media. Printers are purely output devices. Printers are classified into line printers and dot matrix printers. A line printer prints one line of information simultaneously, whereas a dot matrix printer prints one character at a time. A dot matrix printer uses a 5 X 7 or 7 X 9 dot matrix formation to represent each character. Dot matrix printers therefore provide a broken appearance to the characters, whereas a line printer provides a better quality output. A line printer has a speed of about 2000 lines per minute whereas a dot matrix printer has a lower speed of approximately 100 characters per second. If we talke about credit card printer than they need to have a merchant accounts with which credit card processing done. In big shopping mall credit card machine are available there.  With credit card software  and credit card terminal they use credit card printer  to for day to day functions.

Daisy wheel printers and letter quality printers are also character printers. But they produce excellent quality output. However, they are more expensive and slower than dot matrix printers. All the printers discussed so far are called impact printers as they make physical contact with paper while printing. A no impact printer on the other hand transfers information to paper without any physical contact. Example of no impact printers is laser printers, xerographic printers, electrostatic printers, etc.

 

Many printers are primarily used as local peripherals, and are attached by a printer cable or, in most new printers, a USB cable to a computer which serves as a document source. Some printers, commonly known as network printers, have built-in network interfaces (typically wireless or Ethernet), and can serve as a hardcopy device for any user on the network. Individual printers are often designed to support both local and network connected users at the same time.

Input and Output Devices-2

Terminals have become very popular interactive input and output units. A terminal, when connected to a CPU, sends data and instructions directly into the computer. Terminals can be classified into two types, namely, hard copy terminals and soft copy terminals. A hard copy terminal provides a print out on paper whereas a soft copy terminal provides a visual display on a screen. A soft copy terminal is also known as a CRT (Cathode Ray Tube) terminal.

 

Key-to-tape, key-to-disk and key-to-diskette are stand alone data entry stations. There units usually have a small processor attached to a key board and a visual display unit. The processor checks for the accuracy of data at the time of entry. The screen displays what is being entered. There facilities are highly desirable for a data processing centre. Hence most of the data processing centres are switching over from punched card input to data entry stations.

 

A graphic display terminal displays information in both character and graphic forms. These are extensively used for CAD/CAM (computer aided design/computer aided manufacture) applications.

A potter is used to obtain printed copies of graphic outputs. It is used by architects and designers to produce blueprints of their design on paper.

Input and Output Devices-1

Still today we have already discussed different computer hardware parts. In our last talk we have discussed on magnetic disk. The Diskettes and Winchester disks provide random access memory on micro-computers. A diskette is a smaller disk of 5¼ inch in diameter. It provides a storage capacity of 360 KB and an average access time of 180 milli seconds. Today we are going to discuss one other and important part of computer hardware and that is input and Output devices.  

 

Input and Output Devices 

The input or output units of a computer system establish the communication between the system and its users. A large number of input and output units are available in the market. A few of them are discussed in this note.

 

Punched card is the most ancient (few decades old) input medium. Instruction and data punched on cards are transmitted into a computer through a card reader. A printed card had survived a whole century because of its simplicity. But it is on its way out now. Punched cards are being replaced by terminals which provide direct data entry. In next post we will discuss briefly on input and output devices.

 

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