Книга: Introduction to Microprocessors and Microcontrollers

Let’s start by looking at a system

The word ‘system’ is used to describe any organization or device that includes three features.

A system must have at least one input, one output and must do something, i.e. it must contain a process. Often there are many inputs and outputs. Some of the outputs are required and some are waste products. To a greater or lesser extent, all processes generate some waste heat. Figure 1.1 shows these requirements.

Figure 1.1 The essential requirements of a system

A wide range of different devices meets these simple requirements. For example, a motor car will usually require fuel, water for cooling purposes and a battery to start the engine and provide for the lights and instruments. Its process it to burn the fuel and extract the energy to provide transportation for people and goods. The outputs are the wanted movement and the unwanted pollutants such as gases, heat, water vapour and noise.

The motor car contains other systems within it. In Figure 1.2, we added electricity as a required input to start the engine and provide the lights and the instruments but thereafter the battery is recharged by the engine. There must, then, be an electrical system at work, as in Figure 1.3, so it is quite possible for systems to have smaller systems inside or embedded within them. In a similar way, a motor car is just a part of the transport system.

Figure 1.2 An everyday system

Figure 1.3 Recharging the battery

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