The processor (also called central processing unit, or CPU) is the part of the computer that actually works with the data and runs the programs. There are two main processor types in common usage today: CISC and RISC. Some computers have more than one processor and are thus called "multiprocessor". This is distinct from multitasking. Advertisers often use megahertz numbers as a means of showing a processor's speed. This is often extremely misleading; megahertz numbers are more or less meaningless when compared across different types of processors.