Unfortunately, QBasic1.1, QuickBasic 4.5 and QB64 do not have built in Boolean data types. Here are three techniques showing how to use Boolean logic within QBasic / QB64.
Code Download
QBT20_1.BAS
QBT20_2.BAS
QBT20_3.BAS
QB64 is a free download at www.qb64.com
QB64 Wiki & Manual is found at qb64.com/wiki.html
QBasic 1.1 comes with OldDOS. A zip file of OldDOS can be found at www.pcxt-micro.com/download.html
QBasic 1.1 needs DOSBox to run on Windows Vista and greater, Mac, and Linux.
DosBox is a free download at www.dosbox.com
Free QB64/QBasic Code
QBasic.Net - www.qbasic.net
Pete's QBasic Site - www.petesqbsite.com/index.php
QB45 - qb45.org
Phatcode - games.phatcode.net