Boolean

Overview

The simple type boolean is a logical data type. Data of type boolean has one of only two values, either true or false. A boolean variable is 1 byte in size.

The true value can be assigned directly to a boolean variable or from the result of a comparison or test that was successful (true). Similarly the false value can be assigned directly or from the result of a comparison or test that was not successful (false). The Write() and Writeln() procedures will print a string that corresponds to the value of a boolean variable (either "TRUE" or "FALSE"). A Boolean variable can be used as the expression in an if statement. The WriteStr() procedure can be used to store a string literal representing a boolean variable's value in a string variable.

program booleantest;
var
    tooLarge   : Boolean = false;
    boolString : ShortString;
begin
  Writeln(tooLarge);
  tooLarge := (0 = 0);
  Writeln(tooLarge);
  tooLarge := (3 > 5);
  Writeln(tooLarge);
  tooLarge := true;
  Writeln(tooLarge);
  if tooLarge then
    Writeln('tooLarge is true')
  else
    Writeln('tooLarge is false');
  WriteStr(boolString,tooLarge);
  Writeln(boolString);
end.

Outputs:
FALSE

TRUE
FALSE
TRUE
tooLarge is true
TRUE

See also

• Boolean Expressions

From the Free Pascal wiki, page "Boolean", as it stood on 2020-10-14 after a change by Rfc1394, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's Licensing page. If you have concerns about this material, message the admin.