Sun Studio 12 Update 1: Fortran User's Guide

2.2.5 Separate Compiling and Linking

You can compile and link in separate steps. The -c option compiles source files and generates .o object files, but does not create an executable. Without the -c option the compiler will invoke the linker. By splitting the compile and link steps in this manner, a complete recompilation is not needed just to fix one file, as shown in the following example:

Compile one file and link with others in separate steps:

demo% f95 -c file1.f                          (Make new object file)
demo% f95 -o prgrm file1.o file2.o file3.o         (Make executable file)

Be sure that the link step lists all the object files needed to make the complete program. If any object files are missing from this step, the link will fail with undefined external reference errors (missing routines).