Every computerized function in today's devices is implemented using one or multiple microprocessors, meaning a computer processor (central processing unit, or CPU) usually contained in a single integrated circuit (IC). The microprocessor comprises at least the arithmetic logic unit (ALU) and control circuitry, but logically also registers, and input/output (I/O) banks, in addition to more advanced features commonly tailored to a specific product category (wearables, low power sensors, mixed signal, ...) or market (consumer, medical, automotive, ...).

At this point in history, almost all microprocessors are found in embedded systems. Even though people are likely to possess a computer, laptop, and smartphone, maybe even a tablet, the number of embedded microprocessors in a given household far dwarfs the number of general-purpose microprocessors.

Even within a laptop or PC, there are a number of embedded microprocessors in addition to its general-purpose CPU. These microprocessors have tasks like handling keyboard or mouse input, processing touch-screen inputs, converting streams of data into Ethernet packages, or creating video or audio output.

In older systems, such as the Commodore 64, this same pattern can be seen, with a CPU IC, sound IC, video IC, and so on. Whereas the CPU runs whatever code the application developer has written, the other chips in the system have very specific purposes, down to the controller IC for the floppy or hard disk drive.

Outside of general-purpose computers, we find embedded microprocessors everywhere, often in the form of even further integrated MCUs. They control kitchen devices, washing machines, and the engines of our cars, in addition to the higher-level functions and the processing of sensor information.

While the first microwaves were analog devices, using mechanical timers and variable resistors to set power level and duration, today's microwaves contain at least one microcontroller, which is responsible for handling user input, driving a display of some type, and configuring the microwave's systems. The display itself can have its own microcontroller, depending on the complexity of the chosen configuration.

Perhaps more excitingly, embedded systems also provide monitoring, automation and fail-safe features that keep airplanes flying, ensure that guided missiles and space rockets perform as intended, and enable ever-increasing possibilities in areas such as medicine and robotics. The avionics of an airplane constantly monitor countless parameters from a multitude of sensors, running the same code on its triple-redundant configuration to detect any possible glitches.

Tiny yet powerful microprocessors enable the rapid analysis of chemicals and DNA or RNA strands, which would have taken racks of equipment before. With the progress of technology, an embedded system has become small enough that it can be sent through the human body to monitor its health.

Beyond Earth, space probes and rovers on Mars, the Moon, and asteroids are performing a myriad of duties every day, again with the courtesy of well-tested embedded systems. The Moon missions themselves were made possible due to the first major example of an embedded system in the form of the Apollo Guidance Computer. This 1966-era embedded system consisted of wire-wrapped boards full of triple-input NOR logic gates, built for the explicit purpose of handling navigation, guidance, and control of the Command Module and Lunar Module launched by the Saturn V rockets.

The ubiquitous and versatile nature of embedded systems has made them an inseparable part of modern life.

For embedded systems, they are usually distinguished between the following categories: