true -- a constant with the value of 1

okay=true 

The constant true can be assigned to variables which will later appear in conditions (e.g. an if-statement.
true may also be written as TRUE or even TrUe.

input "Please enter a string of all upper letters: " a$ 
if (is_upper(a$)) print "Okay" 

sub is_upper(a$) 
	if (a$=upper$(a$)) return true 
	return false 
end sub