Copyright Goodheart-Willcox Co., Inc. 14 Introduction to Microsoft Offi ce Processing Processing of the data takes place between the input and the output. Processing is the transformation of input data and acting on those data. In principle, processing is very simple: additions and decisions. These two instructions are used to load programs and data, follow instructions, and produce output. More complex actions are developed using these two basic functions. The result is called the instruction set for a central processing unit. The basic instruction set is different for each central processing unit. Central Processing Unit The central processing unit (CPU) is the device that fetches coded instructions, decodes them, and then runs or executes them. The CPU is also called a microprocessor or chip. Although it is about the size of a thumbnail, the CPU contains billions of circuits. See Figure 1-11. Due to their constant execution of actions, CPUs generate a lot of heat. To help prevent the CPU from overheating, fans are often mounted directly above them to help circulate air. Many computers contain multiple CPUs. The CPU controls all jobs performed by the computer’s other parts. The user runs a program, and its instructions set the CPU’s list of jobs. The CPU has two primary components: the arithmetic/logic unit and the control unit. Motherboard The CPU and memory are both mounted on a larger printed circuit board called the motherboard or the system board. The motherboard connects all the hardware in the computer. It provides the electrical connections through which all data are transferred between hardware devices. The three main components on the motherboard are the processor, memory, and expansion ports/slots. A port is a point of interface between the motherboard and external devices. Universal serial bus (USB) is an industry standard for communication between devices and the computer. Output Output is data provided to the user. An output device produces an action based on the instructions from the CPU. The most common output device is a computer monitor. This device formats the 1s and 0s the CPU uses into human-readable material. Speakers output audio based on the 1s and 0s generated by the CPU. FYI Many stand-alone monitors contain USB ports on the side so peripherals can be attached without needing to reach the computer box. RomboStudio/Shutterstock.com Figure 1-11. A CPU being inserted into a socket on the motherboard.