g77 is the GNU Fortran
compiler, part of the GCC
"GNU Compiler Collection
". It allows users to compile Fortran77
code, with the common extensions from f77
Like all the GNU compilers, g77 consists of two main modules. The GNU Back End, the code generator that takes RTL intermediate language and generates assembly language output, and is shared between C, C++, Java and others. Also, there is the Fortran Front End, unique to g77, that converts Fortran into RTL.
Runtime support for Fortran is provided by libg2c, which is automatically linked by g77.