Individualized exercises are a promising feature in promoting modern e-learning. The focus of this article is on the QuizPACK system, which is able to generate parameterized exercises for the C language and automatically evaluate the correctness of student answers. We introduce QuizPACK and present the results of its comprehensive classroom evaluation during four consecutive semesters. Our studies demonstrate that when QuizPACK is used for out-of-class self-assessment, it is an exceptional learning tool. The students' work with QuizPACK significantly improved their knowledge of semantics and positively affected higher-level knowledge and skills. The students themselves praised the system highly as a learning tool. We also demonstrated that the use of the system in self-assessment mode can be significantly increased by basing later classroom paper-and-pencil quizzes on QuizPACK questions, motivating students to practice them more.