Input and Output Devices

Input devices are used to transmit data to the CPU. If we wanted to add a series of number using the computer, the number to be added would be transmitted to the CPU by one of the following devices.
The computer terminal, perhaps, the most common input device in computer system (it is also used as an output device). It consists of a keyboard and a screen called CRT (Cathode Ray Tube). If punched cards are used as input in a particular computer system, then an input device known as a card reader is needed. The card reader “reads” the data in the punched holes by using wire brushes or light beam. It then converts, or changes, this data into electronic signals or pulses which can be understood by the computer.

The console is a computer terminal that has special functions. The computer operator uses this machine for several purposes. He or she can control the other manhines in the system and can enter input by means of the console. The operator can use the console to communicate with the other users by sending messages from the console to the individual terminals in the system.
Another input device that is used in some systems is called a Magnetic Ink Character Reader (MIRC). This machine “reads” characters made with magnetized ink and transmits the data to the CPU. Characters made with magnetic ink are readable by both humans and machines. A bank, for example, would use MIRC to input the account number on the bottom of a person check.

An input device that is used more and more frequently is the optical scanner or the optical mark recognition device. It is referred to as “optical” because it works in a way that is not dissimilar to the human eye works. Such as machine “reads” coded symbols and transmits them as an electrical signal to the CPU. Many standardized tests are graded by a computer. The data from these tests are entered by means of an optical mark recognition device. Many supermarkets use optical scanners prices and keep current inventories.

A magnetic tape drive is used to convert data stored ass magnetic tape into electrical signals which can be understood by the CPU as it function is as an input device. It can also be used as an output device when it is used to record output from the CPU on magnetic tape.

Other sophisticated input devices will become quite common in the near future. Voice input devices, for example which is also called speech recognition devices, will be a very popular input method. Handicapped people will be able to communicate with the CPU in some systems by means of eye movements. Although such input devices are very advanced, they will be seen often in computer systems over the next few years.

There are several types of output devices. Some of them, such as tape and disk drive and terminals, are used as input devices. When a terminal or video monitor is used as an output device, the information displayed on the screen is called sofy copy. This means that the information shown is temporary. Another kind of output device is needed to obtain a permanent copy of the information.

The device used to get a printed, permanent copy, or hard copy of the information is called a printer. Printers are divided into two major types: Impact and non impact. When an impact printer receive signals from the CPU, the characters in the printer strike the paper in much the same way as those in a typewriter hit the paper. Some of these printers print only one character at a time, although they can print approximately 900 characters a minute. Other impact printers, called line printers, print one line at a time.

Non impact printers are newer than impact printers. These printers operate by means of heat and heat-sensitive paper, electrical charges (positive or negative), or by laser beams. Some non impact printers can print to 5.000 lines per minute. In addition to being faster than impact printers, they will probably replace impact printers in the years to come because they can print special characters and can be used with special forms.

A plotter is a special kind of device that, like impact and non impact printers, also produces hard copy. It is used to display output in graphic, or picture form. Instead of actually printing the output, the plotter draws it.
The output device used in conjunction with punched cards is called a card punch. This machine receives signals from the CPU and converts these signals into the hollerith code. The coded information is then punched onto cards.

A. Answer the following questions based on the text above
1. Mention the components of computer system!
2. What special function does a console have?
3. What is the optical mark recognition used for?
4. How does a computer grade tests?
5. What is meant by MIRC?
6. What is the difference between soft copy and hard copy?
7. How does a card punch work?
8. Will non impact printers replace impact printers? Why?
9. “This machine receives......” What does “This” refer to?
10. What is used to display output in graphic, or picture form?