What does terminal generally refer to?

Terminal generally refers to a computer or computer system, a machine used to allow users to input data and display their calculation results; some terminals are fully electronic, and some are electromechanical, also known as terminals machine, which is different from a stand-alone computer.

Terminal (English: Computer terminal) is a computer or computer system that allows users to input data and display its calculation results. Some terminals are fully electronic, while others are electromechanical. Also known as a terminal, it is different from a stand-alone computer.

(An ASCII video terminal around 1982)

The terminal is actually an input and output device, which is an external device compared to the computer host. Assume that it does not provide computing processing functions by itself. Early computer terminals were generally electromechanical teletypes, such as the ASR33. But they are too slow for most applications. In the early 1970s, many computer companies realized that television input terminals were much better than punch cards and could make computers easier for users to interact with, leading to new applications. The problem at that time was that the memory required to display a page of text was too large compared to the small computers of the time. Before the widespread use of integrated circuits, the speed required to display television signals posed too high a technical challenge to the logic gates of the time. At that time, a company announced that it would produce a $15,000 video terminal and attracted many buyers, but in the end its engineers decided that the plan could not be completed. Another solution was the storage tube invented by Tektronix, a machine that could display the information output to it, but could not refresh it.

Early video terminals used special logic gates and did not have their own central processing unit. One of the motivations for developing microprocessors was to simplify the complexity of electronic components in terminals. Most terminals have green or orange screens and are connected to mainframe computers. A typical terminal connects to a host computer using serial data communications such as RS-232, and IBM uses its own system network architecture protocol to connect its host computer to the terminal via coaxial cable.

Later so-called smart terminals (such as VT52 and VT100) were introduced. There are still many emulation softwares for these two terminals available today. These terminals are called "intelligent" because they understand escape sequences and can position the cursor and control display position. Important non-VT100 terminals were the IBM 3270, various Wisdom models, and the Tektronix 4014. In the 1970s there were more than a dozen terminal manufacturers in the world, and most terminals had incompatible commands. The most important terminal manufacturers in the 1970s and early 1980s were Digital, Wisdom, Televideo, Lil Sigler, and Heathkit.

Although the early IBM personal computers also used a green display screen, they were not considered terminals. The PC's display screen does not include any letter-generating hardware; all video signals are generated in the PC's graphics card. But using appropriate emulation programs a personal computer can be connected to a mainframe computer to emulate a terminal. The final use of microprocessors in personal computers greatly eliminated the need for terminals. Most Telnet clients for today's personal computers provide emulation of the most common terminal (generally VT100). [1

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