is predefined constant, its ordinal value is 1 for Boolean. Where ByteBool, 1 is the default, but any non-zero value is acceptable. However, displaying the ord() of ByteBool will either return 0 or 1, as it masks back to Boolean. This is true for WordBool and LongBool also. 

Begin
   While True do {.. do something forever ..}
End.

Source: Reserved Words

See Also:

false, const.