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 the use of if...else statements in C programming. However, if you're looking to solidify your knowledge and demonstrate your proficiency in C programming, consider enrolling in our C certification course.

What are 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.

1. if … else statements in C

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.

Read More - Top 50 C Interview Questions and Answers

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

When you want to print any code only upon the satisfaction of a given condition, go with the simple if statement.

Flow Chart:

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 in the C Compiler 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

It is an extension of the if statement. Here, there is an if block and an else block. When one wants to print output for both cases - true and false, use the if-else statement.

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

It is an extension of the if-else statement. If we want to check multiple conditions if the first “if” condition becomes false, use the if else-if ladder. If all the if conditions become false the else block gets executed.

Flow Chart:

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

We can include an if-else block in the body of another if-else block. This becomes a nested if-else statement.

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
}

  #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;
}

10 is even

switch(expression){ 
case value1: 
//code to be executed; 
break; //optional 
case value2: 
//code to be executed; 
break; //optional 
...... 
default: 
code to be executed if all cases are not matched; 
} 

#include <stdio.h>

int main() 
{ 
	int var = 3; 

	switch (var) { 
	case 1: 
		printf("Case 1 is executed"); 
		break; 
	case 2: 
		printf("Case 2 is executed"); 
		break; 
	case 3: 
		printf("Case 3 is executed"); 
		break; 
	default: 
		printf("Default Case is executed"); 
		break; 
	} 
	return 0; 
}

Case 3 is executed

testexpression? expression1 : expression2;

#include <stdio.h>
int main() {
   int a = -4;
   double b = 29.42;
   int c = a? printf("True value : %lf",b):printf("False value : 0");
   return 0;
}

True value: 29.420000

//loop or switch case 
break;

#include <stdio.h>
main( ){
   int i;
   for (i=1; i<=5; i++){
      printf ("%d ", i );
      if (i==5)
      break;
   }
}

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//loop statements 
continue; 
//some lines of the code which is to be skipped

#include <stdio.h>
int main( ){
   int i;
   for (i=1; i<=8; i++){
      if (i==5)
      continue;
      printf("%d ", i);
   }
   return 0;
}

1 2 3 4 6 7 8

goto label;
// ...
label:
// Statement(s) to execute

#include <stdio.h>
int main( ) {
   printf("Welcome ");
   goto l1;
   printf("How's the experience?");
   l1: printf("to ScholarHat");
   return 0;
}

Welcome to ScholarHat

return expression;

#include <stdio.h>
int multiply(int x, int y) {
 return x * y;
}
int main() {
 int z = multiply(8,9);
 printf("The product is: %d\n", z);
 return 0;  
}

The product is: 72