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4.2 Options Controlling Fortran Dialect

The following options control the dialect of Fortran that the compiler accepts:

Specify the layout used by the the source file. The free form layout was introduced in Fortran 90. Fixed form was traditionally used in older Fortran programs.

Set the "DOUBLE PRECISION" type to an 8 byte wide.

Set the default integer and logical types to an 8 byte wide type. Do nothing if this is already the default.

Set the default real type to an 8 byte wide type. Do nothing if this is already the default.

Allow `$' as a valid character in a symbol name.


Compile switch to change the interpretation of a backslash from “C”-style escape characters to a single backslash character.

Set column after which characters are ignored in typical fixed-form lines in the source file, and through which spaces are assumed (as if padded to that length) after the ends of short fixed-form lines.

Popular values for n include 72 (the standard and the default), 80 (card image), and 132 (corresponds to “extended-source” options in some popular compilers). n may be `none', meaning that the entire line is meaningful and that continued character constants never have implicit spaces appended to them to fill out the line. -ffixed-line-length-0 means the same thing as -ffixed-line-length-none.

Specify the maximum allowed identifier length. Typical values are 31 (Fortran 95) and 63 (Fortran 200x).

Specify that no implicit typing is allowed, unless overridden by explicit `IMPLICIT' statements. This is the equivalent of adding `implicit none' to the start of every procedure.

Conform to the specified standard. Allowed values for std are `gnu', `f95', `f2003' and `legacy'.