Boolean
Standard data type
Syntax
`
Dim variable As Boolean
`
Description
Boolean data type. Can hold the values `True` or `False`
Default value on initialization is `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.
- 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'.
- Nevertheless the definition under the hood for a FB boolean remains an 1-bit integer, zero extended to fill larger integer types.
- Therefore when assigning a boolean with an integer value (by implicit conversion and not with the `False` or `True` value), '0' induces the `False` state and '1' or '-1' induces the `True` state (any other value also induces the `True` state, but with a warning message).
- Otherwise when assigning a numeric type with a boolean (by implicit conversion), `False` induces the '0' value and `True` induces the '-1' value.
- 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.
Example
`
Dim boolvar As Boolean
boolvar = True
Print "boolvar = ", boolvar
`
Output:

    boolvar =     true

Version

- Since fbc 1.04.0

Dialect Differences

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

Differences from QB

- New to FreeBASIC

See also

- `CBool`
- `True`
- `False`
- `Table with variable types overview, limits and suffixes`