while ( attempt < 3 && !open )

while ( the user has made less than 3 tries AND the lock is NOT open )

Boolean Expression

The Boolean expression

 attempt < 3 && !open 

Should evaluate to true when the user gets the first or another chance, and to false when the user does not get another chance. The table shows how this works:

Number of tries	open	attempt < 3	!open	attempt < 3 && !open	Another Chance?
0	false	true	true	true && true	true
1	false	true	true	true && true	true
1	true	true	false	true && false	false
2	false	true	true	true && true	true
2	true	true	false	true && false	false
3	false	?	?	? && ?	????
3	true	?	?	? && ?	????

The logic in a computer program is often this complicated (or worse!) A chart like this may be necessary to check that the logic is correct.