The Case Control Structure

 

1. The Case Control Structure:

The case control structure is used in C as part of the switch statement. It allows the program to check a value against multiple cases and perform different actions based on the result.

Example:

c
int num = 2; 
switch(num) { 
    case 1: 
        printf("One\n"); 
        break; 
    case 2: 
        printf("Two\n"); 
        break;
    case 3: 
        printf("Three\n"); 
        break; 
    default: 
        printf("Invalid number\n"); 
        break; 
}

Output: Two

Explanation: The switch statement checks the value of num against each case. Since num is equal to 2, the second case is executed, printing "Two".

2. Decisions Using switch:

The switch statement is used in C to make decisions based on the value of a single variable or expression. It can be used as an alternative to a long if-else statement.

Example:

c
char grade = 'B'; 
switch(grade) { 
    case 'A': 
        printf("Excellent\n"); 
        break; 
    case 'B': 
        printf("Good job\n"); 
        break;
    case 'C': 
        printf("Good\n"); 
        break; 
    case 'D': 
        printf("Needs Improvement\n");
        break; 
    default: 
        printf("Invalid grade\n"); 
        break; 
}

Output: Good job

Explanation: The switch statement checks the value of grade against each case. Since grade is equal to 'B', the second case is executed, printing "Good job".

3. Tips and Traps:

When using the switch statement, it's important to remember to include a break statement after each case to prevent the program from executing additional cases. If a break statement is not included, the program will continue to execute the code for each subsequent case.

4. switch Versus if-else Ladder:

The switch statement can be used as an alternative to a long if-else ladder when checking a single variable against multiple conditions. It can make the code more readable and easier to maintain.

Example:

c
int num = 5;
if (num == 1) { 
    printf("One\n"); 
}
else if (num == 2) { 
    printf("Two\n"); 
} 
else if (num == 3) { 
printf("Three\n"); 
} 
else { 
printf("Invalid number\n"); 
}

Output: Invalid number

Example using switch:

c
int num = 5; 
switch(num) { 
    case 1: 
        printf("One\n");
        break; 
    case 2: 
        printf("Two\n"); 
        break; 
    case 3: 
        printf("Three\n"); 
        break; 
    default: 
        printf("Invalid number\n"); 
        break; 
}

Output: Invalid number

5. The goto Keyword:

The goto keyword in C is used to transfer control to a labeled statement within the same function. However, it can make the code harder to understand and maintain, and should generally be avoided.

Example:

c
for (int i = 1; i <= 10; i++) { 
    for (int j = 1; j <= 10; j++) {
        if (i * j == 25) { 
            goto found; 
         } 
     } 
}
printf("Number not found\n"); 
goto end; 
found: 
printf("Number found at %d, %d\n", i, j); 
end:
printf("end");