Fortran: Compile Link, and Run

Compilation is the process which translates high level languages such as Fortran (the syntax of which is independent of the particular machine you are using) into machine code language (which is dependant on the hardware architecture of your individual machine). A large program will almost certainly use many subroutines including some in libraries that are not written by you. These libraries will contain code that is already compiled. Linking connects your program to all the relevant subprograms which you call, resulting in a complete program module which can be directly executed by the machine. Organizing code in libraries means that the linker only has to load the routines called by your program.