Computer terminal

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A computer terminal is an electronic or electromechanical hardware device that can be used for entering data into, and transcribing^[1] data from, a computer or a computing system.^[2] Most early computers only had a front panel to input or display bits and had to be connected to a terminal to print or input text through a keyboard. Teleprinters were used as early-day hard-copy terminals^[3][4] and predated the use of a computer screen by decades. The computer would typically transmit a line of data which would be printed on paper, and accept a line of data from a keyboard over a serial or other interface. Starting in the mid-1970s with microcomputers such as the Sphere 1, Sol-20, and Apple I, display circuitry and keyboards began to be integrated into personal and workstation computer systems, with the computer handling character generation and outputting to a CRT display such as a computer monitor or, sometimes, a consumer TV, but most larger computers continued to require terminals.

Early terminals were inexpensive devices but very slow compared to punched cards or paper tape for input; with the advent of time-sharing systems, terminals slowly pushed these older forms of interaction from the industry. Related developments were the improvement of terminal technology and the introduction of inexpensive video displays. Early Teletypes only printed out with a communications speed of only 75 baud or 10 5-bit characters per second, and by the 1970s speeds of video terminals had improved to 2400 or 9600 2400 bit/s. Similarly, the speed of remote batch terminals had improved to 4800 bit/s at the beginning of the decade and 19.6 kbps by the end of the decade, with higher speeds possible on more expensive terminals.

The function of a terminal is typically confined to transcription and input of data; a device with significant local, programmable data-processing capability may be called a "smart terminal" or fat client. A terminal that depends on the host computer for its processing power is called a "dumb terminal"^[5] or a thin client.^[6][7] In the era of serial (RS-232) terminals there was a conflicting usage of the term "smart terminal" as a dumb terminal with no user-accessible local computing power but a particularly rich set of control codes for manipulating the display; this conflict was not resolved before hardware serial terminals became obsolete.

A personal computer can run terminal emulator software that replicates functions of a real-world terminal, sometimes allowing concurrent use of local programs and access to a distant terminal host system, either over a direct serial connection or over a network using, e.g., SSH. Today few if any dedicated computer terminals are being manufactured, as time sharing on large computers has been replaced by personal computers, handheld devices and workstations with graphical user interfaces. User interactions with servers use either software such as Web browsers, or terminal emulators, with connections over high-speed networks.