The compiler directives can alter the behavior of the compiler.

When the source format is fixed or terminal, a compiler directive shall be written in the program-text area and may be followed only by space characters and an optional inline comment. When the reference format is free-form, a compiler directive may be followed only by space characters and an optional inline comment. When the alternative syntax is used, a compiler directive can be followed by a dot.

Specific directives are described next.