Technical data

Intrinsic Subroutine Extensions
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Intrinsic Subroutine Extensions
This section describes the intrinsic subroutines that are extensions to Fortran
77. The rules for using the intrinsic subroutines are
• The subroutine names are specially recognized by the compiler. A
user-written subroutine with the same name as a system subroutine
must be declared in an EXTERNAL statement in the calling
subprogram.
• Using a user-written subroutine with the same name as a system
subroutine in one subprogram does not preclude using the actual
system subroutine in a different subprogram.
• To pass the name of a system subroutine as an argument to another
subprogram, the name of the system subroutine must be declared in an
INTRINSIC statement in the calling subprogram.
• When a system subroutine name is passed as an argument to another
subprogram, the call to the system subroutine via the formal parameter
name in the receiving subprogram must use the primary calling
sequence for the subprogram (when there is more than one possible
calling sequence).
a. The library function time can be invoked only if it is declared in an external statement.
Otherwise, it will be misinterpreted as the VMS-compatible intrinsic subroutine time.