Standard data type


Dim variable As Boolean


Boolean data type. Can hold the values True or False.

Notes on definition of boolean data type: Ideally, the definition of the boolean data type is that it holds the value of True or False, and that's it. However, to make this concept a reality, we need a definition that uses real world connections. A more realistic definition is that the boolean data type is a 1-bit integer, having the value 0 to indicate False and 1 to indicate True. For a practical definition, we must consider, yet again, additional factors. The most significant factor is that the hardware (processor) on which code is executed does not directly support a 1-bit data type; the smallest register or memory size we can work with is 8-bits or 1-byte. Therefore, a practical definition of boolean data type is an integer, 8 bits wide, having the value 0 or 1, where all other values are undefined. However, because of longstanding differences between C/C++ and FB with respect to logical operations, the interpretation of the value must also be considered. Assume "false" is 0 in both C/C++ and FB. C/C++ has logical 'not' operator '!' such that '!0' produces '1'. FB has a bitwise Not operator such that 'not 0' produces '-1'. Therefore the definition for a C/C++ boolean is an unsigned 1-bit integer, zero extended to fill larger integer types, and the definition for a FB boolean is a signed 1-bit integer, sign extended to fill larger integer types. However, the purpose and intent of the boolean data type remains, that it should only ever hold a True value or False value, regardless of the underlying details.


Dim boolvar As Boolean
boolvar = True
Print "boolvar = ", boolvar

boolvar =     true

Dialect Differences

  • Not available in the -lang qb dialect unless referenced with the alias __Boolean.

Differences from QB

  • New to FreeBASIC

See also