Open Watcom FORTRAN 77 Language Reference

FORTRAN Statements
2.9 CALL Statement
CALL sub [( [a [, a] ... ] )]
where:
sub
a
is a symbolic name of a subroutine and must not be the name of a main program, function,
common block, or block data subprogram. As an extension to FORTRAN 77, Open Watcom
FORTRAN 77 permits the calling of functions.
is an actual argument.
The CALL statement is used to invoke the execution of a subroutine subprogram or function.
Example:
X = 1.0
Y = 1.1
Z = 1.2
CALL QUAD( X, Y, Z )
.
.
.
END
SUBROUTINE QUAD( ARGA, ARGB, ARGC )
REAL ARGA, ARGB, ARGC
PRINT *, 2.0*ARGA**2 + 4.0*ARGB + ARGC
END
In the above example, the variables X, Y and Z are passed to the subroutine QUAD. This subroutine
computes an expression and prints the result.
Notes:
1. The parameters in the CALL statement are called actual arguments.
2. The parameters in the SUBROUTINE statement are called dummy arguments.
3. The actual arguments in a subroutine or function reference must agree in order, number and
type with the corresponding dummy arguments.
4. An actual argument may be an expression, array name, intrinsic function name, external
procedure name (i.e., a subroutine or function name), a dummy procedure name (i.e., one that
was an argument to the calling subroutine or function), or an alternate return specifier
(subroutines only). An alternate return specifier takes the form *s, where s is the statement
label of an executable statement that appears in the same program unit as the CALL statement.
An expression may not be a character expression involving the concatenation of an operand
whose length specification is (*) unless the operand is the symbolic name of a constant.
5. Actual arguments are associated with dummy arguments by passing the address of the actual
arguments.
CALL Statement 23