Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In computer central processing units, micro-operations, also known as a micro-ops or ¿ops, are detailed low-level instructions used in some designs to implement complex machine instructions (sometimes termed macro-instructions in this context). Various forms of ¿ops have long been the basis for traditional microcode routines used to simplify the implementation of a particular CPU design or perhaps just the sequencing of certain multi-step operations or addressing modes. More recently, ¿ops have also been employed in a different way in order to let modern "CISC" processors more easily handle asynchronous parallel and speculative execution: As with traditional microcode, one or more table lookups (or equivalent) is done to locate the appropriate ¿op-sequence based on the encoding and semantics of the machine instruction (the decoding or translation step), however, instead of having rigid ¿op-sequences controlling the CPU directly from a microcode-ROM, ¿ops are here dynamically issued, that is, buffered in rather long sequences before being executed.