bit wise operator

[Amon Ra]

i dont understand what that line does..i know what the & does, but i dont understand why there is the 0x00FF

localaddress->h_addr_list[0][3] & 0x00FF 

coul anybody explain to me? thanks in advance

[jim mcnamara]

& tiwddles bits, && does a boolean operation.

The 0xFF thing has the last 8 bits on,

& then twiddles the last 8 bits of array element to on.

[Amon Ra]

so lets say that the array element == -3..
then when i do the & 0xFF, what does it become?

[riis]

The 0x00FF thing is called a mask. You can compare the working of these masks with the usage of masks in drawing programs.

The & operator doesn't turn the last 8 bits of the array element on, but retrieves for you the last 8 bits of that array element.

A quick example:

arrayEl: 0010 1010 1101 0001
mask:    0000 0000 1111 1111   &

result:  0000 0000 1101 0001

[riis]

-3:      1111 1111 1111 1100
mask:    0000 0000 1111 1111   &

result:  0000 0000 1111 1100

The value of result is 252. The mask is 255 (0x00FF), but NEVER use this for regular calculations. Since the & operator is a bitwise operator, you can only use it to set or retrieve bits.