The escin function determines whether an input key is defined. It returns a non-zero value (TRUE) if the input key is defined, or zero (FALSE) otherwise.
The key constants you pass to escin are the same ones that getkey returns, and are defined in the include file <cbase\escape.h>.
A common use of escin is to provide alternate key strokes for a function. For example, C/Base programs accept both <F1>h and <HELP> to invoke the help screen. If escin (HELP) returns TRUE (non-zero), C/Base programs replace <F1>h with <HELP> on the function key prompt line.