说明：  These exercises and projects were originally the even-numbered exercises in the first edition. (The first edition did not distinguish between exercises and programming projects.) For the benefit of readers who have the first edition, the original exercise number is given in square brackets. For example,
(These exercises and projects were originally the even-numbered exercises in the first edition. (The first edition did not distinguish between exercises and programming projects.) For the benefit of readers who have the first edition, the original exercise number is given in square rackets. For example, the notation [was #4] indicates that the number of the exercise (or programming project) was 4 in the first edition. If an answer is different because of second-edition changes, the word "modified" will appear inside the brackets: [was #4; modified].)