Introduction to text terminals

Most KCML programs execute under the control of a terminal with a screen on which the program can print information and a keyboard from which it can receive input. On UNIX versions provided that a program does not attempt to read a keyboard then it can run in the background detached from a terminal.

KCML arranges that all terminals look to application programs as if they were a standard 8 bit ASCII terminal with 16 dedicated function keys, four arrow keys and a range of editing keys such as CANCEL, INSERT, DELETE, NEXT, PREV all of which can be shifted. A number of such virtual function keys are defined in KCML for use in KEYIN, LINPUT, LINPUT LINE, LINPUT LIST and the program editor. The function keys are additional to the 256 possible ordinary keys and will usually be multi-character sequences. The 16 dedicated keys are labelled 0 to 15, and 16 to 31 when shifted. The KEYIN statement reports this number as the value of the character and can jump to a different line number to signify that the key is a function key. The following editing keys return similar higher numbers: