All variables should be initialised before use and a value should never be assumed to have been assigned by the system. This is best done at execution time by simple assignment rather than with data statements since if the application is part of a monolith then the initialisation only takes place when that monolith is first loaded, not each time the application is invoked. Values which are to be retained and used by successive invocations of a subroutine should be declared with SAVE for the benefit of other programmers if not for the compiler.