if-else and ladder if-else in C

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If statement have an optional else block. Here, we must noticed that, if and else block cannot be executed simultaneously. See the below syntax of if...else statement.

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Quick links

• How if...else statement works?
• Example of if...else
• Ladder if...else...if

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Syntax:

if (Condition) {
  // statements to be executed if the condition is true
}
else {
  // statements to be executed if the condition is false
}

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How if...else statement works?

• If condition returns true then the statements inside the body of  “if” are executed and the statements inside body of “else” are skipped.
• If condition returns false then the statements inside the body of  “if” are skipped and the statements in “else” are executed.

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Flow chart of if...else statement:

Flow chart of if...else statement in C

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Example 1: If...else Statement

Let's understand with a simple example to check whether a number is even or odd using if-else statement.

/* Program to check whether a number is even or odd using if-else */
#include <stdio.h>   
int main(){    

int number=0;    
printf("enter a number:");    
scanf("%d",&number);     

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

else{    
 printf("%d is odd number", number);    
}     
return 0;  
}

Output:

Enter a number:14
14 is even number

In above, when the user enter number 14 the condition (number % 2 == 0) is returns true. Hence, the statement inside the body of "if" is executed.

Remember: In C, Zero (0) is used to represent false, and one (1) is used to represent true

Note: If there is only one statement is present in the “if” or “else” body then you do not need to use the braces (parenthesis). Have a look at the below example.

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The above program can also be written like this 👇👇:

#include <stdio.h>   
 int main(){    
 
 int number=0;    
 printf("enter a number:");    
 scanf("%d", &number);     
 
 if(number%2==0)    
   printf("%d is even number", number);     
 
 else    
   printf("%d is odd number", number);      
 
 return 0;  
}

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Ladder if...else...if statement:

It is used in the scenario where there are multiple cases to be performed for different conditions. In if-else-if ladder statement, if a condition is true then the statements defined in the if block will be executed, otherwise if some other condition is true then the statements defined in the else-if block will be executed, at the last if none of the condition is true then the statements defined in the else block will be executed. There are multiple else-if blocks possible. It is similar to the switch case statement where the default is executed instead of else block if none of the cases is matched.

Syntax:

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

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Example 2: Ladder if...else...if statement

#include <stdio.h>   
int main(){    
 int number=0;    
 printf("enter a number:");    
 scanf("%d", &number);     
  if(number==10){    
    printf("number is equals to 10");    
  }    
  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 10, 50 or 100");    
  }    
  return 0;  
}    

Output

Enter a numbr:12
Number is not equal to 10, 50 or 100
Enter a number:50
Number is equal to 50

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Read more about-

• Control statement in C
• Simple if
• Nested if