Abstract: A method and apparatus allowing for the direct manipulation of bit fields contained in a memory source. Logic circuitry performs a process wherein bit segments and bit fields contained in respective data strings are manipulated or moved along respective data strings, wherein the bit fields may not be aligned in accordance with data bytes contained in a respective data string. Additionally, the logic circuitry may mask any bits not associated with either the bit segment and the bit field in the respective data strings. The logic circuitry performs an arithmetic operation, wherein the masked respective data strings are arithmetically coupled to each other providing a resultant data string, the resultant data string containing the arithmetic result of the bit segment and the bit field segment as a bit field result. The logic circuitry can pass forward masks of the bit field result and any partially modified byte(s) instead of an entire mask of the respective data strings.