What is an embedded system? In general, an embedded system is "a device or system that performs a dedicated function and is controlled by an internal computer. An embedded system does not use a general-purpose computer and runs fixed software, or firmware, that is difficult or impossible for the end user to change." Technical people should have no problem understanding the above definition, but non-technical people may have some obstacles. A simpler definition is: "An embedded system is a device that contains a computer that the user is unaware of." However, even this definition requires some explanation. First, most non-IT people's concept of a computer is a beige box with an "Intel-Inside" label on it. Embedded computers are distributed in far more quantities than Intel-x86/Pentium-based desktop PCs. Intel may be "inside", but embedded systems are everywhere. People rarely realize that they often carry several embedded systems with them - in their phones, watches, or smart cards, and they are often unaware of it when interacting with embedded systems in their cars, elevators, kitchen appliances, TVs, VCRs, and entertainment systems. Embedded systems play a more important role in industrial robots, medical equipment, telephone systems, satellites, flight systems, etc. It is the "invisible" feature that distinguishes embedded computers from general-purpose PCs.
Embedded Architecture As a technician, you might want to define embedded systems in terms of architecture. Although most embedded systems are custom built for specific tasks, they are generally made up of the following building blocks: A computer or microcontroller, which may be a measly 4-bit, 8-bit, 16-bit, 32-bit, or even 64-bit. ROM (non-volatile read-only memory) to hold firmware. RAM (volatile random-access memory) to hold program data. I/O ports to connect the microcontroller to switches, buttons, sensors, analog-to-digital converters, controllers, LEDs (light-emitting diodes), and displays. A lightweight embedded operating system, usually written in-house. A specialized single-chip microcontroller is the core of most embedded systems. By integrating several key system components onto a single chip, system designers can create a small, inexpensive computer that can operate with fewer peripherals. The general model of an embedded system is not sufficient to define an embedded system itself. For example, some embedded systems are often not much smaller than a standard PC case. Such devices include: Information query and point-of-sale terminals. Some industrial control systems. Game consoles (such as the Xbox, which is based on x86 and Windows). Digital video recorders (such as the Linux-based TiVo). These devices may use a hard drive to store firmware and run a variety of desktop operating systems such as Windows, Linux, or DOS. This is not a typical embedded system architecture, but according to my earlier definition, they can still be called embedded systems.
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