if else statement in C programming

In the C language decision making statement is executes if the given condition is true otherwise conditional block will never execute.

In C language non-zero and non-null values are consider as true, and zero or null values are consider  false.

if statement

Syntax of an if statement −

if(expression)
 { 
    statements;
 }

In a if statement if the expression result is non zero true, then the block of statement of the ‘if’ statement will be executed. If the expression result is zero, then the block of statement of the ‘if’ statement will not executed and control sent to the next line of if block.

Example: Write a program to demonstrate the ‘if’ statement.

#include 
int main() 
    {
      int x = 10;
      int y = 25;
      if (x < y)	// condition x



OUTPUT



Sum of x+y = 35
 after if statement 




In the above program if(x>y) then the condition will be false and ‘if’ block will never execute.



#include < stdio.h >
   int main() {
      int x = 10;
      int y = 25;
      if (x > y) // condition x>y is false therefore if block will not execute 
      {
         printf("Sum of x+y = %i", (x + y));
      }
      printf("\n after if statement");
      return 0;
   }




OUTPUT



 after if statement




if-else  statement



Syntax of an 'if-else' statement −



if(expression)
{
   statements
}
else
{
   statements
}




In a ‘if-else’ statement if the expression is non zero, then the block of statements of the 'if' statement will be executed. If the statement expression is zero, then the block of code of the 'else' statement will executed.





if else c programming Examples



Example: Write a program to take two numbers from user and find the grater between them using ‘if-else’ statement. 



#include 
   int main()
   {
      int x;
      int y;
      printf("enter  1st number");	
            scanf("%d", & x); // 10	
            printf("enter 2 nd number");
               scanf("%d", & y); // 30
               if (x > y) // check condition x>y 
               {
                  printf("grater value=  %d", x);
               } else {
                  printf("\n grater value=  %d", y);
               }
               return 0;
     }




OUTPUT



enter  1st number 34
enter 2 nd number 2
grater value=  34






Nested  If else



In a C language, we can use if statement inside another if statement(s).



Syntax of an 'nested -if' statement −



if(expression1) {
    statements
	
	If (expression2)
	{	
              statements
	}
}




Example: Write a program to take two numbers from user if both number are between 1 to 9 then print “Good” using nested-if statement. 



#
include < stdio.h >
   int main() {
      int x;
      int y;
      printf("enter  1st number");
      scanf("%d", & x); // 5					
      printf("enter  2nd number");
      scanf("%d", & y); // 7
      if (x < 10) // check condition x<10
      {
         if (y < 10) // nested-if, check condition y<10
         {
            printf("Good");
         }
      }
      return 0;
   }




OUTPUT



enter  1st number3
enter  2nd number2
Good




Nested if else statement



In a C language we
can use if or if-else statement inside another if or 
if-else statement(s).



Syntax of an 'if-else' statement −



if(expression1)
 {
   statements
	
	if (expression2)
	{
	   statements
	}
}
else
{
	if (expression3)
	{	statements
	}

}





Example: Write a program to take three numbers from user and find the grater among them using ‘nested if-else’ statement.



#include 
   int main() {
      int n1, n2, n3;
      printf("Enter three numbers: ");
      scanf("%d %d %d", &n1, &n2, &n3);
      if (n1 >= n2) {
         if (n1 >= n3) {
            printf("The largest number= %d", n1);
         } else {
            printf("The largest number = %d ", n3);
            }
         } else {
            if (n2 >= n3) {
               printf("The largest number= %d", n2);
            } else {
               printf("The largest number=%d", n3);
            }
         }
         return 0;
      }




OUTPUT



Enter three numbers:
20
10
30
The largest number= 30




If else ladder



some times if can be nested inside else as below



if (expression1) {
   statements;
} else {
   if (expression2)
   {
        statements;
   }
   else {
         if (expression3) 
          {
               statements;
          }
      }

   }

}





above statements can be written as 



if (expression1) {
   statements;
} else if (expression2) {

   statements;
} else if (expression3) {
  statements;
}
else
{
  statements;
}





#include 
   int main() {
      int per;
      printf("Enter your percentage of marks: ");
      scanf("%d", &per);
      if (per>90) {
               printf("Your Gread is O");
            }
       else if (per>80) {
               printf("Your Gread is E");
            }
       else if (per>70) {
               printf("Your Gread is A");
            }
            else if (per>60) {
               printf("Your Gread is B");
            }
            else if (per>50) {
               printf("Your Gread is C");
            }
            else if (per>40) {
               printf("Your Gread is D");
            }
            else if (per>30) {
               printf("Your Gread is F");
            }
            
         return 0;
      }



OUTPUT



Enter your percentage of marks:91
 Your Gread is O