What is the use of adding underscore suffix? - FORTRAN

What is the use of adding underscore suffix?

- The compiler of the FORTRAN keeps on appending a trailer underscore with the routine names.

- They have this underscore both in subroutine and in function definitions as well. This way by calling them will help in maintaining the trials.

- By adding the underscore suffix it prevents the two names that are associated with the user-written routines from clashing.

- It also prevents the routines that are associated with the system libraries to interact with each other.

- It prevents the mixed language programming from producing the error and doesn’t allow the linker to have the problems.