Registers Fastest Memory

Register Memory

In a computer, a register is one of a small set of data holding places that are part of a computer processor . A register may hold a computer instruction , a storage address, or any kind of data (such as a bit sequence or individual characters). Some instructions specify registers as part of the instruction.Register is a quickly accessible location available to a digital  processor's central processing unit (CPU).although some registers have specific hardware functions, and may be read-only or write-only. Registers are typically addressed by mechanisms other than main memory, but may in some cases be memory mapped.

Processor registers are normally at the top of the memory hierarchy, and provide the fastest way to access data. The term normally refers only to the group of registers that are directly encoded as part of an instruction, as defined by the instruction set. However, modern high-performance CPU's often have duplicates of these "architectural registers" in order to improve performance via register renaming, allowing parallel and speculative execution.

The number of registers available on a processor and the operations that can be performed using those registers has a significant impact on the efficiency of code generated by optimizing compiler. The strahler number of an expression tree gives the minimum number of registers required to evaluate that expression tree.