Switch-Case in C

Introduction

In the C programming language, the switch-case statement is used to perform different actions based on different conditions. It provides a convenient way to handle multiple cases without using multiple if-else statements. The switch statement evaluates an expression and compares it with various constant values, executing the block of code associated with the matching value.

Syntax

The basic syntax of the switch-case statement in C is as follows:

switch (expression) {
  case constant1:
    // code to execute when expression matches constant1
    break;
  case constant2:
    // code to execute when expression matches constant2
    break;
  // more cases can be added
  default:
    // code to execute when expression doesn't match any constant
}

Working of the switch-case Statement

When the switch statement is encountered, the expression is evaluated. The resulting value is then compared with the constant values specified in the case labels. If a match is found, the corresponding block of code is executed. The break statement is used to exit the switch block and prevent the execution of subsequent case blocks.

If no match is found, the code inside the default block is executed (if provided). The default block is optional and acts as a catch-all case.

Example

Let's look at an example that demonstrates the usage of switch-case in C:

#include <stdio.h>

int main() {
  int choice;
  printf("Enter a number between 1 and 3: ");
  scanf("%d", &choice);

  switch (choice) {
    case 1:
      printf("You entered 1.\n");
      break;
    case 2:
      printf("You entered 2.\n");
      break;
    case 3:
      printf("You entered 3.\n");
      break;
    default:
      printf("Invalid choice.\n");
  }

  return 0;
}

In this example, the user is prompted to enter a number between 1 and 3. The value is then stored in the choice variable. The switch statement evaluates the value of choice and executes the corresponding block of code based on the matching case. If the user enters 1, 2, or 3, the program displays a corresponding message. Otherwise, if the user enters any other value, the program displays an "Invalid choice" message using the default case.

Multiple Cases

In C, multiple cases can share the same block of code. This can be achieved by omitting the break statement after each case except for the last one in the group. The code will then fall through to the next case until a break statement is encountered.

int day = 3;

switch (day) {
  case 1:
  case 2:
  case 3:
    printf("Weekday\n");
    break;
  case 4:
  case 5:
    printf("Weekend\n");
    break;
}

In this example, if day is 1, 2, or 3, the program will output "Weekday." If day is 4 or 5, the program will output "Weekend."

Conclusion

The switch-case statement in C provides an efficient way to handle multiple cases based on a single expression. It helps avoid nested if-else statements and improves code readability. Remember to use the break statement after each case to prevent the execution from falling through to the next case block. In next lesson, we'll learn another control flow statements, the iterative statements. Happy coding!

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