Exams are scored in terms of points intended to be equivalent to one objective-style question each. In summary, a lecture hour corresponds to 4 points and your score is based on the percentage of 100 points you earn. For example, suppose the first quiz has exactly 27 multiple-choice questions, each worth one point. Student A gets 24 right. As an extreme example, say the second quiz has only five questions, each requiring a drawing and a paragraph of text.
Partial credit is given for incomplete answers.
For the final, one set of questions, simple true-false, might be marked as worth 0.5 point per question, other more complicated questions as 2 points per question, etc. The end-points of this conversion are adjusted according to our best estimate of how the individual quizzes compared in difficulty to corresponding quizzes in previous years.