Logical Data Representations

Logical data lengths can be 1-, 2-, 4-, or 8-bytes in length.

The default data size used for a LOGICAL data declaration is LOGICAL(4) (same as LOGICAL(KIND=4)), unless the -integer_size 16 or -integer_size 64 option was specified.

To improve performance on Itanium®-based systems, use LOGICAL(4) (or LOGICAL(8)) rather than LOGICAL(2) or LOGICAL(1).

LOGICAL(KIND=1) values are stored in 1 byte. In addition to having logical values .TRUE. and .FALSE., LOGICAL(1) data can also have values in the range -128 to 127. Logical variables can also be interpreted as integer data.

In addition to LOGICAL(1), logical values can also be stored in 2 (LOGICAL(2)), 4 (LOGICAL(4)), or 8 (LOGICAL(8)) contiguous bytes, starting on an arbitrary byte boundary.

If the -fpscomp nological compiler option is set (the default), the low-order bit determines whether the logical value is true or false. Specify -fpscomp logical for Microsoft* Fortran PowerStation logical values, where 0 (zero) is false and non-zero values are true.

LOGICAL(1), LOGICAL(2), LOGICAL(4), and LOGICAL(8) data representation (when -fpscomp nological option was set) appears below:

LOGICAL(1), LOGICAL(2), LOGICAL(4), and LOGICAL(8) Data Representations