Embedded software is computer software, written to control machines or devices that are not typically thought of as computers, commonly known as embedded systems. It is typically specialized for the particular hardware that it runs on and has time and memory constraints. This term is sometimes used interchangeably with firmware.
A precise and stable characteristic feature is that no or not all functions of embedded software are initiated/controlled via a human interface, but through machine-interfaces instead.
Manufacturers build embedded software into the electronics of cars, telephones, modems, robots, appliances, toys, security systems, pacemakers, televisions and set-top boxes, and digital watches, for example. This software can be very simple, such as lighting controls running on an 8-bit microcontroller with a few kilobytes of memory with the suitable level of processing complexity determined with a Probably Approximately Correct Computation framework (a methodology based on randomized algorithms). However, embedded software can become very sophisticated in applications such as routers, optical network elements, airplanes, missiles, and process control systems.
Unlike standard computers that generally use an operating systems such as macOS, Windows or Linux, embedded software may use no operating system. When they do use one, a wide variety of operating systems can be chosen from, typically a real-time operating system. Code for embedded software is typically written in C or C++, but various high-level programming languages, such as Java, Python and JavaScript, are now also in common use to target microcontrollers and embedded systems. Assembly languages are often used too, especially in booting and interrupt handling. Ada is used in some military and aviation projects.
Most consumers are familiar with application software that provide functionality on a computer. However embedded software is often less visible, but no less complicated.