Switch Case

1. Which of the following statements are true.

1. Every switch statement requires a default

Ans: False. You can write a switch case with no default.

2. switch(4.2 > 3.14) is a valid switch control expression.

Ans: True. Relational operator will evaluate to an int value 0 or 1.

3. break makes the control jump out of current code block.

Ans: True

4. break can be used to terminate a program.

Ans: False. break will cause control to jump out of current code block. It will not terminate the program.

5. If control expression matches a case label then control will jump to that case and then to default case since default matches everything.

Ans: False. Default case is executed only if no other case labels match OR if there are no break statements and control advances linearly to default case.

 

 

2. Write a program using switch case that takes day of the week (1-7) as user input and prints the name of the day, Monday for 1, Tuesday for 2, and so on. In case user input is outside the range 1-7, program should print an error message using default case.

 

#include <stdio.h>

int main (int argc, char * argv[]) {
    int day = 0;
    printf("Enter day of week [1-7]: ");
    scanf("%d",&day);

    switch(day) {
        case 1:
            printf("Monday\n");
            break;
        case 2:
            printf("Tuesday\n");
            break;
        case 3:
            printf("Wednesday\n");
            break;
        case 4:
            printf("Thursday\n");
            break;
        case 5:
            printf("Friday\n");
            break;
        case 6:
            printf("Saturday\n");
            break;
        case 7:
            printf("Sunday\n");
            break;
        default:
            printf("Invalid input\n");
    }
    return 0;
}

 

 

3. Write a program using switch case that takes year as input and prints the name of cricket world cup winning country for that year,

  1. 1975: West Indies
  2. 1979: West Indies
  3. 1983: India
  4. 1987: Australia
  5. 1992: Pakistan
  6. 1996: Sri Lanka
  7. 1999: Australia
  8. 2003: Australia
  9. 2007: Australia
  10. 2011: India
  11. 2015: Australia

If world cup was not played in the year entered by the user, program should print an error message.

 

#include <stdio.h>

int main (int argc, char * argv[]) {
    int year = 0;
    printf("Enter year of world cup: ");
    scanf("%d",&year);

    switch(year) {
        case 1975:
            printf("West Indies won the world cup in 1975\n");
            break;
        case 1979:
            printf("West Indies won the world cup in 1979\n");
            break;
        case 1983:
            printf("India won the world cup in 1983\n");
            break;
        case 1987:
            printf("Australia won the world cup in 1987\n");
            break;
        case 1992:
            printf("Pakistan won the world cup in 1992\n");
            break;
        case 1996:
            printf("Sri Lanka won the world cup in 1996\n");
            break;
        case 1999:
            printf("Australia won the world cup in 1999\n");
            break;
        case 2003:
            printf("Australia won the world cup in 2003\n");
            break;
        case 2007:
            printf("Australia won the world cup in 2007\n");
            break;
        case 2011:
            printf("India won the world cup in 2011\n");
            break;
        case 2015:
            printf("Australia won the world cup in 2015\n");
            break;
        default:
            printf("There was no world cup played in %d\n", year);
    }

    return 0;
}

 

 

4. Trace the control flow of following program for user inputs listed below.

  1. 4
  2. 5
  3. 9
  4. 11
  5. 3

 

01: #include <stdio.h>

02: int main (int argc, char * argv[]) {
03:     int test = 0;
04:     printf("Enter a value[1-9]: ");
05:     scanf("%d",&test);
06:     printf("You entered ");

07:     switch(test) {
08:         case 9:
09:            printf("9\n");
10:            break;
11:         case 3:
12:             printf("3\n");
13:         default:
14:             printf("Default\n");
15:         case 4:
16:             printf("4\n");
17:         case 5:
18:             printf("5\n");
19:             break;
20:         case 6:
21:             printf("6\n");
22:             break;
23:     }

24:     return 0;
25: }

4

  1. After user input control reaches line 07. test has value 4. switch control expression evaluates to 4. Control jumps to label 4, line 15.
  2. Control advances to line 16, message 4 is printed. There is no break statement so control advances to line 17.
  3. Control enters case 5, line 18. Message 5 is printed. Control advances to line 19. break statement causes control to jump out of switch case, line 24.
  4. Program terminates.

 

5

  1. After user input control reaches line 07. test has value 5. switch control expression evaluates to 5. Control jumps to label 4, line 17.
  2. Control advances to line 18, message 5 is printed.
  3. Control advances to line 19. break statement causes control to jump out of switch case, line 24.
  4. Program terminates.

 

9

  1. After user input control reaches line 07. test has value 9. switch control expression evaluates to 9. Control jumps to label 9, line 08.
  2. Control advances to line 09. Message 9 is printed.
  3. Control advances to line 10. break statement causes control to jump out of switch case, line 24.
  4. Program terminates.

 

11

  1. After user input control reaches line 07. test has value 11. switch control expression evaluates to 11. Since there is no matching label, control jumps to default case, line 13.
  2. Control advances to line 14. Message default is printed.
  3. Control advances to line 15 and enters case 4.
  4. Control advances to line 16. Message 4 is printed.
  5. Control advances to line 17. Control enters case 5, line 18.
  6. Message 5 is printed. Control advances to line 19. break statement causes control to jump out of switch case, line 24.
  7. Program terminates.

 

3

  1. After user input control reaches line 07. test has value 3. switch control expression evaluates to 3. Control jumps to label 3, line 11.
  2. Control advances to line 12. Message 3 is printed.
  3. Control advances to line 13 and enter default case.
  4. Control advances to line 14. Message default is printed.
  5. Control advances to line 15 and enters case 4.
  6. Control advances to line 16. Message 4 is printed.
  7. Control advances to line 17. Control enters case 5, line 18.
  8. Message 5 is printed. Control advances to line 19. break statement causes control to jump out of switch case, line 24.
  9. Program terminates.

 

 

5. Trace the control flow of the program below for following user inputs

  1. 99
  2. 100
  3. 7
  4. 49

 

01: #include <stdio.h>
02: int main (int argc, char * argv[]) {
03:     int percentile = 0;
04:     printf("Enter your percentile [1-99]: ");
05:     scanf("%d",&percentile);

06:     switch(percentile/10) {
07:         case 9:
08:             printf("Wow, you are among top 10% \n");
09:             break;
10:         case 8:
11:             printf("Good job, among top 20% \n");
12:             break;
13:         case 7:
14:             printf("Decent show, among top 30% \n");
15:             break;
16:         case 6:
17:         case 5:
18:             printf("Pull up your socks \n");
19:             break;
20:         case 4:
21:         case 3:
22:         case 2:
23:         case 1:
24:         case 0:
25:             printf("You should attempt again \n");
26:             break;
27:         default:
28:             printf("Value out of range\n");
29:     }

30:     return 0;
31: }

99

  1. After user input, control reaches line 06. percentile has value 99. switch control expression evaluates to 9 – recall integer division yields quotient. Control jumps to matching case label, line 07.
  2. Control advances to line 08. Message Wow, you are among top 10% is printed.
  3. Control advances to line 09. break causes control to jump out of switch case, line 30.
  4. Program terminates.

 

100

  1. After user input, control reaches line 06. percentile has value 100. switch control expression evaluates to 10. There is no matching case label, control jumps to default case line 27.
  2. Control advances to line 28. Message Value out of range is printed.
  3. Control advances to end of switch case and to line 30.
  4. Program terminates.

 

7

  1. After user input, control reaches line 06. percentile has value 7. switch control expression evaluates to 0. Control jumps to matching case label, line 24.
  2. Control advances to line 25. Message You should attempt again is printed.
  3. Control advances to line 26. break causes control to jump out of switch case, line 30.
  4. Program terminates.

 

49

  1. After user input, control reaches line 06. percentile has value 49. switch control expression evaluates to 4. Control jumps to matching case label, line 20.
  2. There is no break statement so control falls through line 21, 22, 23, 24.
  3. Control advances to line 25. Message You should attempt again is printed.
  4. Control advances to line 26. break causes control to jump out of switch case, line 30.
  5. Program terminates.

 

 

6. Rewrite the world cup winning team program such that there is only one print statement for each winning country.

#include <stdio.h>

int main (int argc, char * argv[]) {
    int year = 0;
    printf("Enter year of world cup: ");
    scanf("%d",&year);

    switch(year) {
        case 1975:
        case 1979:
            printf("West Indies won the world cup in %d\n", year);
            break;
        case 1983:
        case 2011:
            printf("India won the world cup in %d\n", year);
            break;
        case 1987:
        case 1999:
        case 2003:
        case 2007:
        case 2015:
            printf("Australia won the world cup in %d\n", year);
            break;
        case 1992:
            printf("Pakistan won the world cup in %d\n", year);
            break;
        case 1996:
            printf("Sri Lanka won the world cup in %d\n", year);
            break;
        default:
            printf("There was no world cup played in %d\n", year);
    }

    return 0;
}

 

 

7. Trace control flow of above program for following user inputs

  1. temperature = 3 and coolant_level = 4
  2. temperature = 1 and coolant_level = 4
  3. temperature = 1 and coolant_level = 3

 

01: #include <stdio.h>

02: int main(int argc, char * argv[]) {
03:     int temperature = 0, coolant_level = 0;
04:     printf("Enter reactor temperature [1]hot [2]warm [3]cold ");
05:     scanf("%d", &temperature);
06:     printf("Enter coolant level [1]high [2]medium [3]low ");
07:     scanf("%d", &coolant_level);

08:     switch (temperature) {
09:         case 3:
10:             printf("Kick back and have a coffee!");
11:             break;
12:         case 2:
13:             printf("Keep eyes open for any changes");
14:             break;
15:         case 1:
16:             switch (coolant_level) {
17:                 case 1:
18:                     printf("Good job. Keep it full");
19:                     break;
20:                 case 2:
21:                     printf("Quick, fill up the coolant");
22:                     break;
23:                 case 3:
24:                     printf("Run for your life");
25:                     break;
26:                 default:
27:                     printf("Invalid input");
28:                     break;
29:             }
30:             break;
31:         default:
32:             printf("Invalid input");
33:             break;
34:     }

35:     return 0;
36: }

temperature = 3 and coolant_level = 4

  1. After user input control reaches line 08. Value of temperature is 3. Hence control expression evaluates to 3. Control jumps to matching case, line 09.
  2. Control advances to line 10. Message Kick back and have a coffee! is printed.
  3. Control advances to line 11. break causes control to jump out of switch case – line 35.
  4. Program terminates.

 

temperature = 1 and coolant_level = 4

  1. After user input control reaches line 08. Value of temperature is 1. Hence control expression evaluates to 1. Control jumps to matching case, line 15.
  2. Control advances to line 16. Control expression of nested switch evaluates to value of coolant_level, i.e. 4. There is no matching case, control jumps to default case, line 26.
  3. Control advances to line 27. Message Invalid input is printed.
  4. Control advances to line 28. break causes control to jump out of nested switch case, line 30.
  5. break causes control to jump out of outer switch case, line 35.
  6. Program terminates.

 

temperature = 1 and coolant_level = 3

  1. After user input control reaches line 08. Value of temperature is 1. Hence control expression evaluates to 1. Control jumps to matching case, line 15.
  2. Control advances to line 16. Control expression of nested switch evaluates to value of coolant_level, i.e. 3. Control jumps to matching case, line 23.
  3. Control advances to line 24. Message Run for your life is printed.
  4. Control advances to line 25. break causes control to jump out of nested switch case, line 30.
  5. break causes control to jump out of outer switch case, line 35.
  6. Program terminates.