Thread: Is This Site's Tutorial on Bitwise Operation Correct?

I'm reading Alex's tutorial on Bitwise operation on this website.
I'm a bit confused (no pun intended) with this following description which seems incorrect:

***

The leftshift operator is the equivalent of moving all the bits of a number a specified number of places to the left:[variable]<<[number of places]
For instance, consider the number 8 written in binary 00001000. If we wanted to shift it to the left 2 places, we'd end up with 00100000; everything is moved to the left two places, and zeros are added as padding. This is the number 32 -- in fact, left shifting is the equivalent of multiplying by a power of two.

Code:

int mult_by_pow_2(int number, int power)
{
    return number<<power;
}

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Specifically the line in red.
It appears to me this is incorrect; that the leftshift operator is the equivalent of multiplying by two (not by the power of two).
So 8<<1 is 8*2 or 16. 8<<2 is 8*2*2 or 32. Where as 8^2 (8 to the power of 2) is actually 64.

Am I somehow mis-interpreting this?
Thanks

Within limits, m << n is the equivalent to m * 2^n (where 2^n means 2 raised to the power n).

I see. Maybe I would have understood it better if it had said "left shifting is equivalent to multiplying by an additional power of 2."

Thanks

Originally Posted by FloridaJo

I see. Maybe I would have understood it better if it had said "left shifting is equivalent to multiplying by an additional power of 2."

Thanks

Weird but true, left shifting in any base is equivalent to multiplying by a power of whatever the base is. Going to the right is the equivalent of division by that number.

eg. base 10 : 156 * 10 = 1560;

Same thing in base 12 : 110 * 10 = 1100 ( same as 156 * base = left shift ).

Hope that is helpful!