C if..else Statement

In this tutorial, you will find out about if statement (including if…else and settled if..else) in C programming with the help of examples.

C if Statement

The syntax of the if statement in C programming is:

if (test expression) 
{
   // statements to be executed if the test expression is true
}

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How if statement works?

The if statement evaluates the test articulation inside the enclosure ().

If the test expression is evaluated to valid, explanations inside the body of if are executed.

If the test expression is evaluated to bogus, explanations inside the group 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.

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Example 1: if statement

// Program to display a number if it is negative

#include <stdio.h>
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.

When the user enters -2, the test expression number<0 is evaluated to true. Hence, You entered -2 is displayed on the screen.

Output 2

Enter an integer: 5
The if statement is easy.

When the client enters 5, the test expression number<0 is evaluated to bogus and the announcement inside the assortment of if isn’t executed

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C if..else Statement

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

if (test expression) {
    // statements to be executed if the test expression is true
}
else {
    // statements to be executed if the test expression is false
}

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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.

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Example 2: if…else statement

// Check whether an integer is odd or even

#include <stdio.h>
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.

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C if..else Ladder

The if…else statement executes two distinct codes relying on whether the test articulation is valid or bogus. Some of the time, a decision must be produced using multiple prospects.

The if…else stepping stool permits you to check between numerous test articulations and execute various statements.

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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)
}

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Example 3: C if…else Ladder

// Program to relate two integers using =, > or < symbol

#include <stdio.h>
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

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Nested if..else

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

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Example 4: Nested if…else

This program given below relates two whole numbers 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 <stdio.h>
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;
}

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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) {
    print("Hello");
}
print("Hi");

is equivalent to

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

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Please feel free to give your comment if you face any difficulty here.

C Flow Control