Write a C Program to calculate Base-2 and Base-N logarithm by recursion

By | March 24, 2017

C Program to calculate Base-2 and Base-N logarithm


Write a C Program to calculate Base-2 and Base-N logarithm by recursion. Here’s simple Program to calculate Base-2 and Base-N logarithm using recursion in C Programming Language.


Recursion : :


  • Recursion is the process of repeating items in a self-similar way. In programming languages, if a program allows you to call a function inside the same function, then it is called a recursive call of the function.
  • The C programming language supports recursion, i.e., a function to call itself. But while using recursion, programmers need to be careful to define an exit condition from the function, otherwise it will go into an infinite loop.
  • Recursive functions are very useful to solve many mathematical problems, such as calculating the factorial of a number, generating Fibonacci series, etc.

Equation : :


One can easily calculate the logarithm of any base using the following simple equation:

log.png

Where log k is the function that returns the base-k logarithm of a number, and it can be any real number.


Below is the source code for C Program to calculate Base-2 and Base-N logarithm by recursion which is successfully compiled and run on Windows System to produce desired output as shown below :


SOURCE CODE : :


/* C Program to calculate Base-2 and Base-N logarithm by Recursion  */


#include<stdio.h>
int log2(int num);
int logN(int num, int base);

int main()
{
	int num, base;


	printf("Enter number for Base-2 logarithm :: ");
	scanf("%d",&num);

	printf("\nValue of log base 2 of %d = %d\n",num,log2(num));

	printf("\nEnter any number :");
	scanf("%d",&num);
	printf("Enter base to %d :: ",num);
	scanf("%d",&base);

	printf("\nValue of log base %d of %d = %d\n",base,num,logN(num,base));

	return 0;

}

int log2(int num)
{
      if(num==1)
           return 0;
      return 1 + log2(num/2);
}

int logN(int num,int base)
{
      if(num<base)
           return 0;
     return 1 + logN(num/base,base);
}


OUTPUT  : :


************* OUTPUT **************


************* FIRST RUN ***********

Enter number for Base-2 logarithm :: 100

Value of log base 2 of 100 = 6

Enter any number :10
Enter base to 10 :: 10

Value of log base 10 of 10 = 1



************* SECOND RUN ***********

Enter number for Base-2 logarithm :: 2

Value of log base 2 of 2 = 1

Enter any number :100
Enter base to 100 :: 5

Value of log base 5 of 100 = 2

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