1. Which of the following is not a language?     The set of all the sentences spoken by a certain people. The set of all legal English words. The empty set. The empty string.

2. Which of the following statements is incorrect?     This course you take is taught by Professor Wen-Hsiang Tsai. A better title for this course is the theory of computation. The course of Algorithms is a prerequisite of this course. You have to pass the little quiz of each chapter before you can download the word file (lecture note) of the next chapter.

3. Which of the following statement is correct?     Modus ponens is a technique of inductive proof. The deduction “If he shows up, she will leave. Now, he comes. So, she leaves.” is an example of the syllogism proof technique. Understanding workings of correct programs is equivalent to proving theorems by induction. The deduction “Students attend classes. Billy is a student. So he attends classes.” is an example of the modus ponens proof technique.
4. Which of the following statements is incorrect?     A language is a set. A string is a set. An alphabet is a set. A power set of a set A is a set of all the subsets of A.

5. Which of the following statements is incorrect?     A finite-state system can be modeled by a finite automaton. A lexical analyzer may be modeled by a finite automaton. Problems which can be solved by computer are decidable. Computability is the study of how efficient a problem can be solved by computer.