1. CENTRAL PROCESSING UNIT

2. CPU Does the actual processing in the computer. A single chip called a microprocessor. Composed of an arithmetic and logic unit (ALU) and a control unit. The ALU does the processing. The control unit tells the ALU what to do. In a microprocessor both the ALU and control unit are on the same chip.

3. HOW IT WORKS The CPU executes instructions (individual steps of a computer program). These instructions are in machine language. Different processors use different machine languages. Current processors have multiple cores. These are essentially separate processors which can operate separate threads simultaneously (as long as the O/S and application are designed for this.