The CLEAR statement clears (sets to 0) all local
variables that are not assigned to a common storage area. Variables in a named
common storage area or in the unnamed common storage area are unaffected.
Because CLEAR sets to 0 both assigned and unassigned
variables, it can be usefully invoked at the beginning of a program to prevent
problems caused by unassigned variables.
You can use the COMMON statement to assign variables
to a common storage area. You can use the CLEAR COMMON statement
to clear (reset to 0) all local variables that are assigned to a named common
storage area or to the unnamed common storage area.