Conditional Statements in C: if, if..else, Nested if

Conditional Statements in C: An Overview

If you are a programmer, then you already know how to use if...else statements. If not, it's time to learn! Understanding if...else statements is essential, especially for beginners. After reading this article in the C tutorial, you will have a fundamental understanding regarding use of if...else statement in C programming. However, if you're looking to solidify your knowledge and demonstrate your proficiency in C programming, consider enrolling in ourC certification course.

Conditional Statements in C

The conditional statements are also known as decision-making statements. They are of the type if statement, if-else, if else-if ladder, switch, etc. These statements determine the flow of the program execution.

Why Conditional Statements?

• Dynamically controls the manner of program execution.
• Useful in error and exception handling.
• Check the flow of your program.
• Helps to manage the state of your program.
• Helpful in performing complex calculations.

Types of Conditional Statements in C

In this article we'll discuss the first kind of conditional statement i.e. if...else statements in C. We'll discuss the switch statement in the next tutorial switch Statement in C.

if … else statements

if-else is the first kind of control statement in C. In this, the operations are performed according to some specified condition. The statements inside the body of the if block get executed if and only if the given condition is true.

Variants of if-else statements in C

1. if statement in C
2. if-else statement in C
3. if else-if ladder in C
4. nested if statement in C

1. if statement in C

Syntax

if(test condition){ 
//code to be executed 
} 

Example

  #include<stdio.h> 
int main(){ 
int num=8;
if(num%2==0){ 
printf("%d is even number",num); 
} 
return 0; 
} 

• The above code prints the even number.
• The if statement checks if the user input is odd or even.
• If the number is even, the statement inside the if block gets printed.
• If the given input is odd, nothing gets printed.

Output

8 is even number

2. if-else statement in C

Syntax

if(test condition){ 
//code to be executed if condition is true 
}else{ 
//code to be executed if condition is false 
} 

Example

  #include <stdio.h>
int main() {
 int num = 10;
 if(num < 5) {
 printf("Number is less than 5\n");
 }
 else if(num < 10) {
 printf("Number is between 5 and 9\n");
 }
 else {
 printf("Number is 10 or greater\n");
 }
 return 0;
}

• In the above code, the if condition checks if the num is less than 5
• The given number 10 is greater than 5.
• Therefore, the if block gets skipped.
• The statement inside the else block gets printed.

Output

Number is 10 or greater

3. if else-if ladder in C

Syntax

if(test condition1){ 
//code to be executed if condition1 is true 
}else if(test condition2){ 
//code to be executed if condition2 is true 
} 
else if(test condition3){ 
//code to be executed if condition3 is true 
} 
... 
else{ 
//code to be executed if all the conditions are false 
} 

Example

  #include <stdio.h> 
int main(){ 
int number=5; 
if(number==20){ 
printf("number is equals to 20"); 
} 
else if(number==50){ 
printf("number is equal to 50"); 
} 
else if(number==100){ 
printf("number is equal to 100"); 
} 
else{ 
printf("number is not equal to 20, 50 or 100"); 
} 
return 0; 
} 

• In the given code, the program evaluates multiple conditions.
• If the first if condition becomes false, the control goes to the else-if statements.
• If all the conditions fail, the statement inside the else block gets printed.

Output

number is not equal to 20, 50 or 100

4. Nested if…else statement in C

Syntax

if(test condition1)
{ //if condition1 becomes true
 if(test condition1.1)
 { //code executes if both condition1 and condition 1.1 becomes true
 }
 else
 { //code executes if condition1 is true but condition 1.1 is false
 }
}
else
{ //code executes if condition1 becomes false
}

Example

  #include <stdio.h>
int main()
{
 int a = 10;
 int b = 5;
 if (a > b)
 {
 // control goes to the nested if
 if (a % 2 == 0) {
 printf("%d is even\n",a);
 }
 else {
 printf("%d is odd\n",a);
 }
 }
 else
 {
 printf("%d is not greater than %d\n",a,b);
 }
 return 0;
}

• In the above code, the first if statement checks whether a>b.
• If a is greater than b, the nested if statement is checked.
• If the nested if condition is false, the else statement in the nested if block gets executed.
If the first if statement evaluates to false, the nested if block gets skipped and the else block executes.

Output

10 is even

Summary

if...else statements in C are a crucial part of writing an efficient program. They help to organize code and can account for a variety of conditions using comparison operators and logical operators. If used correctly, if...else statements can save your time from writing multiple lines of code. Knowing how to use them properly is thus essential for any programmer. You can also check out our C Certification Trainingtotest your knowledge and get comfortable with using if...else statements.