In the directory containing the Fortran 77 examples has a number of files named Makefile.incl.[compiler], one for each compiler supported. You have to rename one of these files, depending on which compiler you are using, to Makefile.incl before you can compile the examples. This file contains information concerning the compiler and options to use and this information is used in the Makefile for each example.

General instructions on how to compile Fortran 77 programs with different compilers on Linux can be found in the section Fortran Guide - Linux.