Thread: Mask

In essence, how would you use a unsigned short as a bit mask ?

--What's the best way to print the bits and use/manipulate them ?


Thanks
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>In essence, how would you use a unsigned short as a bit >mask ?

A mask can be used to check if a certain bit, or bits, is set or not.

To check if bit 2 is set (note that bit 0 is the first bit), you need the following mask:

unsigned short mask = 0x04;

To check if bit 2 is set, you could do:

if (variable & mask)
{
/* the bit is set */
}

>What's the best way to print the bits and use/manipulate them?

Manipulation with bits can be done best with the bit-operators, look them up in your C book.

To print a byte in binary, you could do something like:

Code:

    unsigned char value = 0x11; /* just a value */
    unsigned char mask = 0x80;
    unsigned char bits [8];
    int i;

    for (i = 0; i < 8; i++)
    {
        bits [i] = ((value & mask) != 0);
        mask >>= 1; /* shift all bits one to right */
        printf ("%d", bits [i]);
    }