Although the name of the compiler and recommended options may differ from platform to platform, all Unix compilers function in essentially the same way as illustrated in the simple examples below.
To create an executable program, you compile a source file containing a main
program. For example, to compile a Fortran program named
hello.f 
use:
f77 hello.f
If no errors occur, the compiler
creates an executable file named a.out
in the current working directory. Similarly,
to compile and then run a C program use:
cc hello.c
a.out
If your source is divided among separate files, simply specify all files
in the compile command:
f77 main.f func1.f ... funcn.f
The -o name option causes the compiler to name the output file
name instead of a.out.
For example, to compile a Fortran program hello.f and name the resulting
executable hello use:
f77 -o hello hello.f
The -c option suppresses the link-edit phase. The compiler generates
an object file with the extension
.o for each input file and not the a.out file. This is
useful when compiling source files that contain only subprograms, which can
be linked later with other object files. The resulting
object files can then be specified
on the compiler command line:
f77 -c func.f
f77 main.f func.o