Technical data

Chapter 3: Fortran Program Interfaces

Example

The following example shows how a Pascal routine must specify the length

of a character string (which is only implied in a Fortran call).

Fortran call to SAM

C SAM IS A ROUTINE WRITTEN IN FORTRAN

EXTERNAL F

CHARACTER*7 S

INTEGER B(3)

…

CALL SAM (F, B(1), S)

<– Length of S is implicit.

Pascal call to SAM

PROCEDURE F_; EXTERNAL;

S: ARRAY[1..7] OF CHAR;

B: ARRAY[1..3] OF INTEGER;

…

SAM_ (F, B[1], S, 7);

<– Length of S is explicit.

Execution-Time Considerations

Pascal checks certain variables for errors at execution time, whereas Fortran

does not. For example, in a Pascal program, when a reference to an array

exceeds its bounds, the error is ﬂagged (if run-time checks are not

suppressed). Use the f77 –c option if you want a Fortran program to detect

similar errors when you pass data to it from a Pascal program.

Array Handling

Fortran stores arrays in column-major order, where the leftmost subscripts

vary the fastest. Pascal, however, stores arrays in row-major order, with the

rightmost subscript varying the fastest. Also, the default lower bound for

arrays in Fortran is 1. Pascal has no default; the lower bound must be

explicitly speciﬁed. Here is an example of the various layouts: