(Multiplication Via Bit Shifting) Left-shifting an unsigned integer by 1 bit is equivalent to multiplying the value by 2. Write function power2 that takes two integer arguments, number and pow, and calculates number * 2pow Use a shift operator to calculate the result. The program should print the values as integers and as bits.

Question

What will be an ideal response?

Answer 1

```
#include
#include
using namespace std;

void displayBits( unsigned ); // prototype
unsigned power2( unsigned, unsigned ); // prototype

int main()
{
unsigned number;
unsigned pow;
unsigned result;

cout << "Enter two integers: ";
cin >> number >> pow;

cout << "number:\n";
displayBits( number );
cout << "\npower:\n";
displayBits( pow );
result = power2( number, pow );
cout << '\n' << number << " * 2^" << pow << " = " << result << '\n';
displayBits( result );
return 0;
} // end main

// shifting n
unsigned power2( unsigned n, unsigned p )
{
return n << p; // shift n to the left p times
} // end function power2

// display the bits of value
void displayBits( unsigned value )
{
const int SHIFT = 8 * sizeof( unsigned ) - 1;
const unsigned MASK = 1 << SHIFT;

cout << setw( 7 ) << value << " = ";

for ( unsigned c = 1; c <= SHIFT + 1; c++ )
{
cout << ( value & MASK ? '1' : '0' );
value <<= 1; // shift value left by 1

if ( c % 8 == 0 ) // output a space after 8 bits
cout << ' ';
} // end for

cout << endl;
} // end function displayBits
```
Enter two integers: 4 7
number:
4 = 00000000 00000000 00000000 00000100
power:
7 = 00000000 00000000 00000000 00000111
4 * 2^7 = 512
512 = 00000000 00000000 00000010 00000000