To help solidify your understanding of this hour's lesson, you are encouraged to answer the quiz questions and finish the exercises provided in the Workshop before you move to the next lesson. The answers and hints to the questions and exercises are given in Appendix E, "Answers to Quiz Questions and Exercises."
Of the following two statements, which one is the declaration of a union and which one is the definition of union variables?
union a_union {
int x;
char y;
};
union a_union x, y;
What's wrong with the following union declaration?
union automobile {
int year;
char model[8]
float weight;
}
In the following statement, what are the values contained by the two union members?
union u {
int date;
char year;
} a_union = {1997};
Given a structure and a union, what are the sizes of the structure and the union? (Assume that the char data type is 1 byte long and the int data type is 2 bytes long.)
struct s {
int x;
char ch[4];
} a_structure;
union u {
int x;
char ch[4];
} a_union;
Exercises
Rewrite the program in Listing 20.1 by switching the order between the statement in line 15 and the statement in line 17. What do you get after running the rewritten program?
Rewrite the program in Listing 20.2. This time, print out values held by all the members in the info union each time one of the members is assigned an integer.
Write a program to ask the user to enter his or her name. Then ask the user whether he or she is a U.S. citizen. If the answer is Yes, ask the user to enter the name of the state where he or she comes from. Otherwise, ask the user to enter the name of the country he or she comes from. (You're required to use a union in your program.)
Modify the program you wrote in exercise 3. Add a bit field and use it as a flag. If the user is a U.S. citizen, set the bit field to 1. Otherwise, set the bit field to 0. Print out the user's name and the name of country or state by checking the value of the bit field.
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