Setting, Clearing and Copying bits of data
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AND xx will clear the bits in A that are also clear in xx, for example:

       A            xx      after AND xx
   %abcdefgh    %01010101    %0b0d0f0h

OR xx will set the bits in A that are also set in xx, for example:

       A            xx      after OR xx
   %abcdefgh    %01010101    %a1c1e1g1

XOR xx will toggle the bits in A that are set in xx, for example:

       A            xx      after XOR xx
   %abcdefgh    %01010101    %aBcDeFgH

To clear the bits in A that are ''set'' in xx, use both OR and XOR, for
example:

       A            xx      after OR xx  after XOR xx
   %abcdefgh    %01010101    %a1c1e1g1    %a0c0e0g0

You can copy a number of bits to a memory location without changing the
other bits using XOR and AND. For example, to copy the top four bits of A
into a memory location without changing the bottom four bits, use the
following:

                A=12345678  dst=abcdefgh
    XOR dst       ********      abcdefgh
    AND &F0       ****0000      abcdefgh
    XOR dst       1234efgh      abcdefgh
    LD  dst,A     1234efgh      1234efgh

This is much more efficient than code such as:

    PUSH AF
    LD   A,dst:AND &0F:LD dst,A
    POP  AF
    AND  &F0:OR dst:LD dst,A