The Central Processing Unit (CPU) is the brain of a computer. It interprets and executes the basic instructions required for using the computer. Interestingly, the first electronic computers used vacuum tubes for circuitry and consumed up to 200 kilowatts of power. Today’s personal computer processors are microprocessors that use very little power. Microprocessors also contain all the circuits necessary for memory, input/output (I/O), and logic. For this reason, a microprocessor is sometimes referred to as a “computer on a chip.”
How the processor works
The CPU consists of two main parts: the control unit (CU) and the arithmetic logic unit (ALU). The ALU performs arithmetic and logical operations, such as addition, subtraction, multiplication, division, and comparison of numbers. All operations underlying computer applications must be carried out by the ALU. The CU controls the sequence of operations in the computer. It reads and interprets each program instruction stored in memory and then directs the ALU or other components to execute that instruction.
The speed at which the processor executes instructions is measured in megahertz (MHz) or gigahertz (GHz). One MHz equals one million cycles per second; one GHz equals one billion cycles per second. A 3 GHz processor performs 3 billion operations per second. Memory addresses are generated much faster than actual data can be moved to or from memory cells, so faster processors provide shorter wait times when running programs or opening files stored on a hard drive. However, they do not necessarily make your programs run faster.
The CPU is essential for the operation of a computer. It contains the control unit and arithmetic logic unit, which manage the sequence of operations in the computer and perform arithmetic and logical tasks. Processor speed is measured in MHz or GHz—the higher the number, the greater the speed. A faster processor does not necessarily mean that your programs will run faster, but it does mean shorter waiting times when opening files or starting programs.