Alpha terminals were terminals that were limited in their input and output to alphanumeric characters, corresponding to the ASCII character set. Such terminals were used in the seventies and eighties.
Alpha terminals consisted of a screen with a keyboard and, in their simplest form as dumb terminals, could only send, receive, and display single alphanumeric characters. Dumb terminals had no processor, but depended on the computing operation of hosts and mainframes. The later intelligent terminals had a simple processor that supported alphanumerics and display.
Used for communication with the central computer and for database queries, alpha terminals supported the protocols of the connected central computer, as well as single and multi- session operation.
One of the best known alpha terminals is the VT100 from Digital Equipment( DEC), developed in the late 1980s. Another is the well-known 3270 from IBM.