The boolean type is predefined in the Standard package as an enumerated data type with two possible values: false and true.

Syntax:

type boolean is (false, true); 

Description:

The boolean type is used for conditional operations. Boolean objects can be used with any of the relational operators <, >, <=, >=, = or /=.

The default value of any object of the boolean type is false.

Example:

signal Condition: boolean; 
Condition <= true;
if Condition then ...  {is equivalent to: if Condition = true then ...}

Note:

• Boolean values (false and true) are not identical to logical 0 and 1, respectively. In VHDL, the logical 0 and 1 are of the bit type.

See also:

Standard Package