 front-end processors usually means that the supplier takes on full responsibility for hardware, software, and interfaces required to essentially "plug in" his product. From a user's point of view, this approach is highly desirable, since it can save him money, time, and aggravation. When considering a front-end processor from a source other than the supplier of the central computer equipment, the buyer should insist on receiving concrete performance data, drawn from installed systems, to substantiate the supplier's claims. The buyer should be- ware "if" the supplier refuses to back up his claims with actual case studies. As further evidence of proven performance, the buyer should personally contact as many previous users as possible, probing not only for their degree of satisfaction, but also for the extent to which the installed systems reflect his own intended system design and ob- jectives. TERMINAL TECHNOLOGY 4.1 CRT DISPLAY TERMINALS The most significant consideration affecting terminal selection is matching the functional capability of the terminal to the functional requirements of the application. The best evidence of this impor- tance lies in the variety of special-purpose terminals developed for such applications as airline reservations, on-line banking, and bro- kerage transaction processing. The application primarily sets the re- quirements of speed, permissible error rates, input/output medium, information codes, and format storage in a terminal. CRT display terminals employ a TV-like display screen to record and display data. They have a keyboard similar to that of a type- writer (see Fig. 4-1). When a key is depressed, the associated numeric or alphabetic character appears on the screen. The character code may be simultaneously transmitted or it may be stored for subse- quent transmission as part of a word or a complete message. Typi- cally, 1000 characters may be simultaneously displayed on the screen, and character transmission rates are in the range of 110-to-1200 char- acters per second. CRT di