# f66

Tells the compiler to apply FORTRAN 66 semantics.

## Syntax

Linux: | -f66

macOS: | -f66

Windows: | /f66

## Arguments

None

## Default

OFF | The compiler applies Fortran 2018 semantics.

## Description

This option tells the compiler to apply FORTRAN 66 semantics when interpreting language features. This causes the following to occur:

- DO loops are always executed at least once.

- FORTRAN 66 EXTERNAL statement syntax and semantics are allowed.

- If the OPEN statement STATUS specifier is omitted, the default changes to STATUS='NEW' instead of STATUS='UNKNOWN'.

- If the OPEN statement BLANK specifier is omitted, the default changes to BLANK='ZERO' instead of BLANK='NULL'.

## IDE Equivalent

Visual Studio: Language > Enable FORTRAN 66 Semantics

## Alternate Options

None

Parent topic: Compatibility Options