Video Display Terminals is commonly used output device. Video Display Terminals is a combination of TV like device monitor and keyboard it consists of small memory called buffer. The buffer size is equal to the number of characters that can be displayed at a time on the terminals screen. Usually a single image can consist of maximum of 1920 (24 rows * 80 columns) characters. Each character entered through the keyboard is stored in buffer and also displayed simultaneously on CRT monitor. Data is sent to the central computer when the operator pressed an enter key. The advantage of VDT is error correction process is easy as long as data is not transmitted. But the major disadvantage is no hard copy or record of typed information remains when the terminal is switched off.
There are different types of terminals
- Dump terminal
- Smart terminal
- Intelligent terminal
- Dumb terminal: Dumb terminal is standalone keyboard and display screen it sends or record data from central computer. Dumb terminal doesn’t have any storage or processor. The keyed data character is immediately transferred to the processor.
- Smart terminal: Smart terminal comprises of keyboard and display screen a microprocessor chips to perform arithmetic and logic function. Smart terminal has internal storage so the input data can be storage and corrected prior to sending to central computer. But Smart terminal cannot be programmed by a user.
- Intelligent terminal: Intelligent terminal is computer by itself. It is built-in microprocessor that can be programmed by a user to suit the requirement. All the basic data processing occurs locally. Further it can communicate with other terminals.
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