Boolean variables are stored as 16-bit (2-byte) numbers, but they can only be True or False.Boolean variables display as either 

True
or 
False
(when Print is used) or 
#TRUE#
or 
#FALSE#
(when Write # is used). Use the keywords True and False to assign one of the two states to Boolean variables.

When other numeric types are converted to Boolean values, 0 becomes False and all other values become True. When Boolean values are converted to other data types, False becomes 0 and True becomes -1.