Boolean values: Difference between revisions
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=={{header|Fortran}}==
Fortran has a '''logical''' data type which can be set to either '''.true.''' or '''.false.''' or be generated via logical expressions such as <=, etc. Such variables cannot be used in normal arithmetic with operators such as +-*/ but only with logical operators such as .OR. and so on. If via the EQUIVALENCE statement their numerical values (or, bit patterns) are inspected as say an integer, the values may well not be as anticipated and differ between computers and compilers. For instance, on the Burroughs 6700 an '''integer''' variable equivalenced to a '''logical''' variable would appear as '''.true.''' if odd, '''.false.''' if even.
The default storage size of a LOGICAL variable is the same as the default storage size of an INTEGER variable, which for many systems is 32 bits. This is done to simplify calculations of record sizes, or the alignment of variables in COMMON storage areas. It is usually possible to declare variables with certain byte sizes (normally only powers of two) so that LOGICAL*1 or similar declarations may be available. If used however there may arise alignment issues with adjacent variables of other types (such as REAL) that may require padding to even word boundaries for best access. Consider <lang Fortran> TYPE MIXED
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