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If-Else Statement in C

The if-else statement in C is used to execute a block of code based on a condition. If the condition is true, the 'if' block executes; otherwise, the 'else' block executes.

Syntax

if (condition) { // Code executed if condition is true } else { // Code executed if condition is false }

Example

int number = 10; if (number % 2 == 0) { printf("%d is even", number); } else { printf("%d is odd", number); }

How It Works

  • The condition inside parentheses is evaluated first.
  • If the condition is true (non-zero), the 'if' block runs.
  • If the condition is false (zero), the 'else' block runs.
  • The else block is optional.

Nested If-Else

You can place an if-else statement inside another if-else to check multiple conditions.

  • Example: int marks = 75; if (marks >= 90) { printf("Grade A"); } else if (marks >= 75) { printf("Grade B"); } else { printf("Grade C"); }

Tips

  • Always use braces `{}` to avoid errors, even for single statements.
  • Keep conditions simple and readable.
  • Use nested if-else sparingly to reduce complexity.
  • Consider using switch statements for multiple constant comparisons.

Common Mistakes

  • Using `=` (assignment) instead of `==` (equality) in conditions.
  • Omitting braces `{}` for multi-line statements.
  • Confusing the order of if, else if, and else blocks.
  • Writing complex conditions without parentheses, leading to unexpected results.