Wiki source for KeyPgBoolean


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{{fbdoc item="title" value="BOOLEAN"}}----
Standard data type

{{fbdoc item="syntax"}}##
[[KeyPgDim|dim]] //variable// [[KeyPgAs|as]] **Boolean**
##
{{fbdoc item="desc"}}
Boolean data type. Can hold the values ##[[KeyPgTrue|True]]## or ##[[KeyPgFalse|False]]##
Default value on initialization is ##[[KeyPgFalse|False]]##

**Notes on definition of boolean data type:** //Ideally, the definition of the boolean data type is that it holds the value of ##[[KeyPgTrue|True]]## or ##[[KeyPgFalse|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 ##[[KeyPgFalse|False]]## and 1 to indicate ##[[KeyPgTrue|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 ##[[KeyPgOpNot|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 ##[[KeyPgTrue|True]]## value or ##[[KeyPgFalse|False]]## value, regardless of the underlying details.//

{{fbdoc item="ex"}}
{{fbdoc item="filename" value="examples/manual/datatype/boolean.bas"}}%%(freebasic)
Dim boolvar As Boolean
boolvar = True
Print "boolvar = ", boolvar
%%

Output:
%%boolvar = true%%

{{fbdoc item="lang"}}
- Not available in the //[[CompilerOptlang|-lang qb]]// dialect unless referenced with the alias ##**""__Boolean""**##.

{{fbdoc item="diff"}}
- New to ""FreeBASIC""

{{fbdoc item="see"}}
- ##[[KeyPgCbool|Cbool]]##
- ##[[KeyPgTrue|True]]##
- ##[[KeyPgFalse|False]]##

{{fbdoc item="back" value="CatPgStdDataTypes|Standard Data Types"}}
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