Using Fortran 77 and NAG's Fortran Library

The document NAG Fortran Library contains an overview of NAG and information on its use that should be read prior to reading this document. The discussion below assumes that you have configured your UNIX account as described in that document.

In this example we have a simple Fortran77 program in the file gammaTest.f (you can see the listing of this file below). It is a modified version of the example program from NAG to test the Gamma Function evaluation program s14aaf. With this file in the current directory this example consists of the following the steps.

nagshell: Start a shell setup for NAG (requires dot file configuration)
make gammaTest: compiles the gammaTest.f file and makes an executable file called "gammaTest"
gammaTest: Run the Gamma Function test.
exit: Exit the nag shell and return the starting evironment.

The output from a sample terminal session is shown below, followed by a discussion of the steps.

The nagshell alias and environment variables used below are available if you have made the suggested UNIX configuration changes described elsewhere.

<100>% nagshell
<1>% make gammaTest
f77   -o gammaTest gammaTest.f -L/opt/lib/nagfl16df -lnag
gammaTest.f:
 MAIN:
<2>% gammaTest
    5.000D+00   2.400D+01      0
<3>% exit
exit
<101>%

The nagshell command starts a new shell with the correct environment for the NAG Fortran library.
The sample Fortran 77 program that invokes the gamma function is stored in a file named gammaTest.f
The make gammaTest command finds the Fortran 77 source file and creates the executable "gammaTest". Since the source file has an ".f" extension, make uses a suffix rule to invoke the f77 compiler in your path. You may also type f77 command the make file generated using the LINK_NAG environment variable:
```
f77 -o gammaTest gammaTest.f $LINK_NAG
```
The executable is run and it reports the correct result.
Finally, exiting the shell returns us to the parent shell (command number <101>) with its previous environment variable and alias definitions.

Listing of the gammaTest.f sample program

*     S14AAF Example Program Text
*     Mark 14 Revised.  NAG Copyright 1989.
*     .. Parameters ..
      INTEGER          NIN, NOUT
      PARAMETER        (NIN=5,NOUT=6)
*     .. Local Scalars ..
      DOUBLE PRECISION X, Y
      INTEGER          IFAIL
*     .. External Functions ..
      DOUBLE PRECISION S14AAF
      EXTERNAL         S14AAF
*     .. Executable Statements ..
      X = 5.0
      IFAIL = 1
*
      Y = S14AAF(X,IFAIL)
*
      WRITE (NOUT,99999) X, Y, IFAIL
      STOP
*
99999 FORMAT (1X,1P,2D12.3,I7)
      END

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