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19/07/07 - 583 Views - Ratings :   4.5 of 5 / 2 Votes

Level - Advance
      

Question -

Write a program to multiply two number without using any' arithemetic operators (*,+,-,/,%) in C.

Answer -

#include <stdio.h>

long int addition(int a, int b)

{
  int result =   0, carry;
  carry = a&b;

  if(carry)
   {
     result = a^b;
     carry =   carry << 1;
     result = addition(carry, result);
    }
  else
   {
     result =   a^b;
   }

  return result;

}

long int multiply(int a, int b)

{

  int   result=0, i=0;

  while(i != b)
    {
      result = addition(result,a);
      i =   addition(i,1);
     }

   return result;

}

void main()

{

  int   a,b;
  printf("Numbers: ");
  scanf("%d %d",   &a,&b);
  printf("\n\nResult: %ld", multiply(a,b));
  printf("\n");

} 

Explanation -

Well this is not an easy question, what we do in this code is that we add two numbers using binary logic and multiply them using addition logice in a loop or recursion.

This logic is used in digital cirucits which are uses logic gates, so this is an also example of code derived from a digital circuit.

First we implement a function addition which takes two number to be added as parameter. This function adds two number bit by bit and also uses recursion call to add a carry value produced in the last step to next order bit.

Then to find product of two numbers it implemets a function called multiply which uses a loop to add a number again and again to itself to produce a cumulative result value. For eg to multiply A with B and to store result in C, C is intialised to 0 and a is added to it B times.

Answer is not so profound if you understand the explanation above.

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