C program to convert a Decimal number to Binary number.

 #include <stdio.h>
int main()
{
	 int n , rem  , i = 1 , bn = 0 ;
	printf("Enter a positive decimal number : ");
	scanf("%d" , &n);
	
	printf("The binary number of decimal %d is : " , n);
	
	while (n > 0)
	
	{
		rem = n % 2 ;
     	bn +=  (i * rem);
		i = i * 10 ;
		n = n / 2;
		
	}
	
	 printf("%d\n",bn);
	
	return 0 ;
}

C program to find the GCD of two numbers using Recursion.

 #include <stdio.h>

int GCD(int a , int b)
{
	
	
	if (b != 0)
	{
	return GCD(b , a%b );
	
	}
	else
	{
		return a ;
	}
	
	
}
 
int main ()
{
	int n1 , n2 ;
	printf("Enter two integer values : ");
	scanf("%d %d" , &n1 , &n2);
	printf("The gcd of two numbers %d and %d = %d\n" , n1 , n2 , GCD(n1, n2));
	
return 0 ;
}

C program to find the sum of digits of a 5 digit number using recursion.

#include <stdio.h>
int fun(int n)
{
	int i = n % 10 ;
	if (n!=0)
	return i + fun(n/10);
	else 
	return 0 ;
}
int main()
{
	int num;
	printf("Enter any number to find sum of digits: ");
	scanf("%d" , &num);
	printf("Sum of digits of %d = %d" , num , fun(num));
	
	return 0 ; 

}

C program to find the Factorial of a given number using Recursion.

 #include <stdio.h>

int fact(int n )
{
	if(n >= 1)
	return n * fact(n - 1);
	else
	return 1 ;

}



int main()
{
	
	int num;
	printf("Enter an integer : ");
	scanf("%d" , &num);
	printf("Factorial of %d is : %d\n" , num , fact(num));
	
	return 0 ;
	
}

C program to find the sum of the fibonacci series using function.

 

#include <stdio.h>

long double func (int r)
{
	long double first = -1 , second = 1 , sum = 0 , third;
	
	for (int i = 0 ; i < r ; i ++)
	{
		third = first + second ;
		sum = sum + third ;
		first = second;
		second = third ;
	}
	
	return sum ;
	
}


int main()
{
	int range ;
	printf("Enter the range: ");
	scanf("%d" , &range);
	

	printf("Sum of Fibonacci series for given range is: %.0Lf\n" , func(range));
	
	return 0 ;
	
}

C program to find the Factorial of a given number using Functions.

 #include <stdio.h>

int fact(int n)
{
	int facto = 1 ;
	for ( int i = n ; i > 0 ; i--)
	{
	
		facto  = facto * i ;
		
	}
	return facto ;
}

int main ()
{
	int num ;
	printf("Enter a number : ");
	scanf("%d" , &num);
	
	printf("Factorial of a given number %d = %d\n" , num , fact(num) );
	
	return 0 ;
}

Programme in C using Function that returns the sum of all the odd digits.

 #include <stdio.h>
int sneha(int n)
{
	int sum = 0 ;
     while(n != 0)
	{
		int rem = n % 10 ;
		if(rem % 2 != 0)
		{
			sum = sum + rem ;
		}
		n = n / 10 ;
	}
	
	return sum ;
}




int main()
{
	int num ;
	printf("Enter any positive number: ");
	scanf("%d" , &num);
	
	printf("All odd digits sum is: %d\n" , sneha(num));

	
}