Bit Operators: Difference between << and <<= or >> and >>= in c

Please explain to me in detail the difference between << and <<= and as well as >> and >>=. I know how shift opera开发者_开发百科tors work, but I am not so sure about them when it comes to >>= or <<=.

Well << only shifts left. <<= shifts left and assigns.

<<= is to << what += is to +.

EDIT

As suggested by MByD, here is an example

int x = 1;

/* Print 32. */
printf("%d\n", x << 5);

/* x stays the same. */
printf("%d\n", x);

x <<= 5;

/* x has become 32. */
printf("%d\n", x);

In C, and many other languages, you can put = after an operator as a shortcut. Instead of writing...

x = x + 5

...I can write...

x += 5

These are called compound assignment operators. You're just seeing the versions of these for bit shift operations.

x >>= 1

...is the same as...

x = x >> 1

<< can be used on both variables and constants.

5 << 2; // this is ok.
a << 2; // this is ok too.

<<= will change the lvalue, so that:

a <<= 2; // bit-shifts a by two positions.
5 <<= 2; // wrong, 5 is 5 and will always be 5.