In computer architecture, a processor register is a small amount of storage available as part of a digital processor, such as a central processing unit (CPU). Such registers are typically addressed by mechanisms other than main memory and can be accessed faster. Almost all computers, load-store architecture or not, load data from a larger memory into registers where it is used for arithmetic, manipulated or tested by machine instructions. Manipulated data is then often stored back into main memory, either by the same instruction or a subsequent one. Modern processors use either static or dynamic RAM as main memory, with the latter usually accessed via one or more cache levels.