C if. else Statement

The if statement evaluates the test expression inside the parenthesis () .

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• If the test expression is evaluated to true, statements inside the body of if are executed.
• If the test expression is evaluated to false, statements inside the body of if are not executed.

To learn more about when test expression is evaluated to true (non-zero value) and false (0), check relational and logical operators.

Example 1: if statement

// Program to display a number if it is negative #include int main() < int number; printf("Enter an integer: "); scanf("%d", &number); // true if number is less than 0 if (number < 0) < printf("You entered %d.\n", number); >printf("The if statement is easy."); return 0; >

Output 1

Enter an integer: -2 You entered -2. The if statement is easy.

Output 2

Enter an integer: 5 The if statement is easy.

C if. else Statement

The if statement may have an optional else block. The syntax of the if..else statement is:

if (test expression) < // run code if test expression is true >else < // run code if test expression is false >

How if. else statement works?

If the test expression is evaluated to true,

• statements inside the body of if are executed.
• statements inside the body of else are skipped from execution.

If the test expression is evaluated to false,

• statements inside the body of else are executed
• statements inside the body of if are skipped from execution.

Example 2: if. else statement

// Check whether an integer is odd or even #include int main() < int number; printf("Enter an integer: "); scanf("%d", &number); // True if the remainder is 0 if (number%2 == 0) < printf("%d is an even integer.",number); >else < printf("%d is an odd integer.",number); >return 0; >

Output

Enter an integer: 7 7 is an odd integer.

When the user enters 7, the test expression number%2==0 is evaluated to false. Hence, the statement inside the body of else is executed.

C if. else Ladder

The if. else statement executes two different codes depending upon whether the test expression is true or false. Sometimes, a choice has to be made from more than 2 possibilities.

The if. else ladder allows you to check between multiple test expressions and execute different statements.

Syntax of if. else Ladder

if (test expression1) < // statement(s) >else if(test expression2) < // statement(s) >else if (test expression3) < // statement(s) >. . else < // statement(s) >

Example 3: C if. else Ladder

// Program to relate two integers using =, > or < symbol #include int main() < int number1, number2; printf("Enter two integers: "); scanf("%d %d", &number1, &number2); //checks if the two integers are equal. if(number1 == number2) < printf("Result: %d = %d",number1,number2); >//checks if number1 is greater than number2. else if (number1 > number2) < printf("Result: %d >%d", number1, number2); > //checks if both test expressions are false else < printf("Result: %d < %d",number1, number2); >return 0; >

Output

Enter two integers: 12 23 Result: 12 < 23

Nested if. else

It is possible to include an if. else statement inside the body of another if. else statement.

Example 4: Nested if. else

This program given below relates two integers using either < , >and = similar to the if. else ladder's example. However, we will use a nested if. else statement to solve this problem.

#include int main() < int number1, number2; printf("Enter two integers: "); scanf("%d %d", &number1, &number2); if (number1 >= number2) < if (number1 == number2) < printf("Result: %d = %d",number1,number2); >else < printf("Result: %d >%d", number1, number2); > > else < printf("Result: %d < %d",number1, number2); >return 0; >

If the body of an if. else statement has only one statement, you do not need to use brackets <> .

For example, this code

if (a > b) < printf("Hello"); >printf("Hi");

is equivalent to

if (a > b) printf("Hello"); printf("Hi");