What is meant by "bit masking"?

Bit masking means selecting only certain bits from byte(s) that might have many bits set. To examine some bits of a byte, the byte is bitwise “ANDed” with a mask that is a number consisting of only those bits of interest. For instance, to look at the one’s digit (rightmost digit) of the variable flags, you bitwise AND it with a mask of one (the bitwise AND operator in C is &): flags & 1; To set the bits of interest, the number is bitwise “ORed” with the bit mask (the bitwise OR operator in C is |). For instance, you could set the one’s digit of flags like so: flags = flags | 1; Or, equivalently, you could set it like this: flags |= 1; To clear the bits of interest, the number is bitwise ANDed with the one’s complement of the bit mask. The “one’s complement” of a number is the number with all its one bits changed to zeros and all its zero bits changed to ones. The one’s complement operator in C is ~. For instance, you could clear the one’s digit of flags like so: flags = flags & ~1; Or, equivalently, you could clear it like this: flags &= ~1; read less