Boolean data type

Generalities about Boolean Data Type
– Programming languages like Pascal and Java have a built-in Boolean data type.
– Comparison operators like ‘and’ are defined to return a Boolean value.
– Conditional and iterative commands are used to test Boolean-valued expressions.
– Some languages like C90 and Lisp represent truth values using other data types.
– Booleans can be implemented as numerical variables with one binary digit or as bit strings of length one.

Boolean Data Type in Programming Languages
– Fortran:
– The first versions of FORTRAN had no logical values or operations.
– FORTRAN IV introduced a Boolean data type, logical literals, and logical operators.
– FORMAT statements in FORTRAN have specific format descriptors for parsing or formatting logical values.
– Later languages like Modula, Ada, and Haskell adopted the Boolean data type derived from FORTRAN.
– FORTRAN uses a BIT(1) representation for Boolean values.
– C, C++, Objective-C, AWK:
– Initial implementations of C did not have a Boolean type, using integers instead.
– ANSI C added enumerated types, allowing programmers to define their own Boolean types.
– Standard C introduced the _Bool type, which can be used with the bool name and true/false constants.
– C++ has a separate bool data type with automatic conversions from scalar and pointer values.
– Objective-C has a separate BOOL data type, but can also use the _Bool type from C.
– PL/I:
– PL/I does not have a Boolean data type.
– Comparison operators in PL/I generate BIT(1) values, with 0B representing false and 1B representing true.
– Operations on PL/I BIT(1) values are performed on each bit.
– The element-expression of an IF statement in PL/I is true if any bit is 1.
– Rexx:
– Rexx does not have a Boolean data type.
– Comparison operators in Rexx generate 0 or 1, with 0 representing false and 1 representing true.
– Rexx operands must be 0 or 1 for comparison operators.
– Tcl:
– Tcl does not have a separate Boolean type.
– Like in C, integers 0 (false) and 1 (true) are used in Tcl.
– Tcl expressions that evaluate to 1 are considered true.

Introduction and Implementation of BOOLEAN data type in SQL:1999
– SQL:1999 standard introduced BOOLEAN data type as an optional feature.
– Introduced IS (NOT) TRUE, IS (NOT) FALSE, and IS (NOT) UNKNOWN operators.
– SQL BOOLEAN behaves like Booleans in other languages, storing TRUE and FALSE values.
– Nullable BOOLEAN can have the special null value.
– SQL standard defines three literals for BOOLEAN type: TRUE, FALSE, and UNKNOWN.
– Few major SQL systems implement the BOOLEAN feature as of 2012.
– Firebird and PostgreSQL are exceptions, with PostgreSQL using NULL instead of UNKNOWN.
– Microsoft SQL Server does not support BOOLEAN, using BIT data type as a workaround.
– Microsoft Access also uses BIT data type instead of BOOLEAN.
– PostgreSQL has a distinct BOOLEAN type as in the standard.

Treatment of BOOLEAN values in different SQL systems
– Microsoft SQL Server does not support BOOLEAN as a standalone data type.
– Microsoft Access represents TRUE as 1 and does not support the Null tri-state.
– PostgreSQL allows storing predicates directly into a BOOLEAN column.
– MySQL treats BOOLEAN as an alias of TINYINT(1), with non-zero integers considered true.
– Tableau Software has a BOOLEAN data type with True and False literals.

BOOLEAN representation in Forth programming language
– Forth does not have a Boolean type, using regular integers for true and false.
– Value 0 represents false, while -1 represents true in Forth.
– Forth uses one set of logical operators for both mathematical calculations and conditions.

Related topics and references:
– Boolean differential calculus, flag programming, Shannons expansion, three-valued logic, and true/false commands for shell scripting are related topics.
– References include books, programming language documentation, and online tutorials for various languages and SQL systems.