BOOLEAN


Standard data type

Syntax:
dim variable as Boolean

Description:
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.


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

Output:
boolvar =     true


Dialect Differences:
Differences from QB:
See also:
Back to Standard Data Types
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