A compiler directive directs the compiler to do some special action. Directives are also called pragmas.
A compiler directive is inserted into the source program as one or more lines of text. Each line looks like a comment, but has additional characters that identify it as more than a comment for this compiler. For most other compilers, it is treated as a comment, so there is some code portability.
A complete summary of Fortran directives appears in Appendix C, Fortran Directives Summary.