1) Why there is no assignment by logical operator like there is assignment by sum and difference?
bool a = true;
bool b = false;
a = a || b;
a ||= b; // syntax error!
a |= b; // OK.
2) What is the meaning of applying bitwise operator on boolean variable? Is it the same as using logical operator?
It's true that &&= and ||= are "missing" from C. I think one reason is that logical AND and OR in C perform short-circuiting, which would be a little strange in the abbreviated form. But don't use the bitwise assignment operators in their place. Instead, just write:
a = a && b;
c = c || d;
The bitwise operators will work if you have canonical true/false values (1 and 0). But if applied to non-canonical values, such as 5 and 2, you will get different results (5 && 2 is 1, but 5 & 2 is 0).
&& and || means that the second operand is only evaluated if it is needed to determine the result. For example, if you have 0 && x, then x is not evaluated because you already know the answer is 0. Similarly, if you have 1 || y, then y is not evaluated because you already know the answer is 1. This is significant if the second operand is slow to evaluate (e.g., a function call), or has side effects.a |= b means the same as a = (a | b), except that the address of a is evaluated only once. Then you look up the rules for promotion, and for assignment to bool.
