C - What is this syntax about? <<

what does this sybol means please? "<<" fo开发者_如何学Cr example: if (1 << var)

I want the name of the thing to study. Thank you.

It shifts the bits in the integer 1 var positions to the left. So in effect it calculates 2 to the power of var.

See the article on bit shifts on wikipedia.

That is a "left bit shift" operator. In your example, it shifts 0000..00001 left "var" places. So if var is 1, this is the same as "1 << 1" which shifts 0001 to 0010, which is 2. If var was 2 the answer would be 0100 (4), etc. If this isn't making sense, you'll need to read up on binary arithmetic.

That's the left bitwise shift operator.

The other bitwise shift operator is >>.

The name is The C Programming Language.

It is the left shift operator.

You might want to read about bitwise operations, and more specifically, bitshift operators.

<< is a bit manipulation operator. Specifically << performs left shift operation. This achieves the effect of multiplying the underlying value by power of 2.

More information could be found at: http://en.wikipedia.org/wiki/Bit_manipulation