help with a logic algorithm

I need an algorithm that finds the possible states of variables used in "ifs"
for instance, I need to find out possible states:
if (a && b){
   // 'a' is true
   // 'b' is true
}
else
{
   // 'a' maybe be true or false
   // 'b' maybe be true or false
}
More complex:
if (a && b || c){
   // 'a' maybe be true or false
   // 'b' maybe be true or false
   // 'c' maybe be true or false
}
else
{
   // 'a' maybe be true or false
   // 'b' maybe be true or false
   // 'c' maybe be true or false
}
I think this algorithm may already exists.. but not finding it.
Maybe something related with predicates.