A basic instruction for moving a string of bytes in a word has been devised. Because the operations in the instruction are basic, very few variations are necessary to accommodate diversity of lengths and variables. These operations are imbedded in a single code sequence; the compiler can therefore generate exactly the minimum sequence necessary to perform the operations and can precompute many of the operands at compile time, typically completing the instruction within a single cycle time. The control necessary to optimize the operations is then in the compiler instead of the hardware.