visual display unit

/glas T-T-Y/ or /glas ti'tee/ A terminal that has a display screen but which, because of hardware or software limitations, behaves like a teletype or some other printing terminal, thereby combining the disadvantages of both: like a printing terminal, it can't do fancy display hacks, and like a display terminal, it doesn't produce hard copy. An example is the early "dumb" version of Lear-Siegler ADM 3 (without cursor control). See tube, tty; compare dumb terminal, {smart terminal}. See "TV Typewriters" for an interesting true story about a glass tty.

<hardware> (or "smart terminal", "programmable terminal") A terminal that often contains not only a keyboard and screen, but also comes with a disk drive and printer, so it can perform limited processing tasks when not communicating directly with the central computer. Some can be programmed by the user to perform many basic tasks, including both arithmetic and logic operations. In some cases, when the user enters data, the data will be checked for errors and some type of report will be produced. In addition, the valid data that is entered may be stored on the disk, it will be transmitted over communication lines to the central computer. An intelligent terminal may have enough computing capability to draw graphics or to offload some kind of front-end processing from the computer it talks to. The development of workstations and personal computers has made this term and the product it describes semi-obsolescent, but one may still hear variants of the phrase "act like a smart terminal" used to describe the behaviour of workstations or PCs with respect to programs that execute almost entirely out of a remote server's storage, using said devices as displays. The term once meant any terminal with an addressable cursor; the opposite of a glass tty. Today, a terminal with merely an addressable cursor, but with none of the more-powerful features mentioned above, is called a dumb terminal. There is a classic quote from Rob Pike (inventor of the blit terminal): "A smart terminal is not a smart*ass* terminal, but rather a terminal you can educate". This illustrates a common design problem: The attempt to make peripherals (or anything else) intelligent sometimes results in finicky, rigid "special features" that become just so much dead weight if you try to use the device in any way the designer didn't anticipate. Flexibility and programmability, on the other hand, are *really* smart. Compare hook. (1995-04-14)