ON KEY(n) - Event trapping statement that specifies a subroutine to
            branch to when key n is pressed
Syntax
  ON KEY(n) GOSUB {linelabel | linenumber}
    - n, an integer expression, is the number of a function key, direction
      key, or user-defined key
    - linelabel or linenumber is the first line of the event-handling
      subroutine
 
See Also  <KEY(N) ON>  <KEY(N)>