Boolean variables are variables that can only contain two values: TRUE or FALSE. These variables are used for answering questions whose answer is yes or no. var x:boolean; begin x:=true; x:=false; x:=0<5; {is 0 less than 5? yes, it's TRUE} x:=6=7; {is 6 equal to 7? no, it's FALSE} end. See Script:Is prime for an example.