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.