Its just an example of multiplying any number by 2^n-1 or 2^n+1 without using any multiplication symbol.

//multiplication of the number by 2^n+1 2^n-1

#include<stdio.h>

#include<stdlib.h>

#include<conio.h>//will not work in linux

main()

{

      int n=3;

      int m=n<<3;

      printf("%d\n",(m-n));//multiplying 3 by 7

      printf("%d",(m+n));//multiplying 3 by 9

      getch();

      }