Syntax Rules for Compiler Directives

The following syntax rules apply to all general and OpenMP* Fortran compiler directives. You must follow these rules precisely to compile your program properly and obtain meaningful results.

A directive prefix (tag) takes one of the following forms:

General compiler directives:

cDEC$

OpenMP Fortran compiler directives:

c$OMP

c
Is one of the following: C (or c), !, or *.

The following prefix forms can be used in place of cDEC$: cDIR$ or !MS$.

The following are source form rules for directive prefixes:

• In fixed and tab source forms, prefixes begin with C (or c), *, or !.
  The prefix must appear in columns 1 through 5; column 6 must be a blank or a tab¹. From column 7 on, blanks are insignificant, so the directive can be positioned anywhere on the line after column 6.
  
  
• In free source form, prefixes begin with !.
  The prefix can appear in any column, but it cannot be preceded by any nonblank, nontab characters on the same line.
  
  
• In all source forms, directives spelled with two keywords can be separated by an optional space; for example, "LOOP COUNT" and "LOOPCOUNT" are both valid spellings for the same directive. However, when a directive name is preceded by the prefix "NO", this is not considered to be two keywords. For example, "NO PREFETCH" is not a valid spelling; the only valid spelling for this directive is "NOPREFETCH".

A compiler directive ends in column 72 (or column 132, if compiler option extend-source is specified).

General compiler directives cannot be continued. OpenMP Fortran directives can be continued.

A comment beginning with an ! can follow a compiler directive on the same line.

Additional Fortran statements (or directives) cannot appear on the same line as the compiler directive.

Compiler directives cannot appear within a continued Fortran statement.

Blank common used in a compiler directive is specified by two slashes (/ /).

If the source line starts with a valid directive prefix but the directive is not recognized, the compiler displays an informational message and ignores the line.