FORTRAN 77 Language Reference

Source Line Formats

A statement takes one or more lines; the first line is called the initial line; the subsequent lines are called the continuation lines.

You can format a source line in either of two ways:

Standard Fixed Format

The standard fixed format source lines are defined as follows:


The tab-format source lines are defined as follows: @

Mixing Formats

You can format lines both ways in one program unit, but not in the same line.

Continuation Lines

The default maximum number of continuation lines is 99 @ (1 initial and 99 continuation). To change this number of lines, use the -Nln option. @

Extended Lines

To extend the source line length to 132 characters, use the -e option.@ Otherwise, by default, f77 ignores any characters after column 72.

Example: Compile to allow extended lines:

demo% f77 -e prog.f 


Padding is significant in lines such as the two in the following DATA statement:

C        1         2         3         4         5         6         7
     1                              /

Comments and Blank Lines

A line with a c, C, *, d, D, or! in column one is a comment line, except that if the -xld option is set, then the lines starting with D or d are compiled as debug lines. The d, D, and! are nonstandard. @

If you put an exclamation mark (!) in any column of the statement field, except within character literals, then everything after the ! on that line is a comment. @

A totally blank line is a comment line.

Example: c, C, d, D, *,!, and blank comments:

c      Start expression analyzer 
*      Crack the expression:
       IF ( S .GE. '0' .AND. S .LE. '9' ) THEN ! EoL comment 
              CALL PUSH        ! Save on stack. EoL comment 
d             PRINT *, S       ! Debug comment & EoL comment 
              CALL TOLOWER ! To lowercase EoL comment 
       END IF 
D      PRINT *, N!       Debug comment & EoL comment 
C      Finished 
!       expression analyzer


A directive passes information to a compiler in a special form of comment. @ Directives are also called compiler pragmas. There are two kinds of directives:

See the Sun Fortran User's Guide and the Fortran Programming Guide for details on the specific directives available with f77.

General Directives

The form of a general directive is one of the following:@

The variable id identifies the directive keyword; a is an argument.


A directive has the following syntax:

Rules and Restrictions

After the first eight characters, blanks are ignored, and uppercase and lowercase are equivalent, as in FORTRAN text.

Because it is a comment, a directive cannot be continued, but you can have many C$PRAGMA lines, one after the other, as needed.

If a comment satisfies the above syntax, it is expected to contain one or more directives recognized by the compiler; if it does not, a warning is issued.

Parallelization Directives

Parallelization directives explicitly request the compiler attempt to parallelize the DO loop that follows the directive. The syntax differs from general directives. Parallelization directives are only recognized when compilation options --parallel or --explicitpar are used. (f77 parallelization options are described in the Fortran User's Guide.)

Parallelization directives have the following syntax:

Each parallelization directive has its own set of optional qualifiers that follow the keyword.

Example: Specifying a loop with a shared variable:


See the Fortran Programming Guide for details about parallelization and these directives.