Embedded Software

Embedded software is computer software, written to control machines or devices that are not typically thought of as computers. 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, although firmware can also be applied to ROM-based code on a computer, on top of which the OS runs, whereas embedded software is typically the only software on the device in question.

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 in' embedded software in the electronics of e.g. 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), or can become very sophisticated in applications such as airplanes, missiles, and process control systems.

Unlike standard computers that generally use an operating systems such as OS X, Windows or GNU/Linux, embedded software may use no operating system, or when they do use, a wide variety of operating systems can be chosen from, typically a real-time operating system. This runs from small one-person operations consisting of a run loop and a timer, to LynxOS, VxWorks, BeRTOS, ThreadX, to Windows CE or Linux (with patched kernel). Others include OpenWrt, PikeOS, eCos, Fusion RTOS, Nucleus RTOS, RTEMS, INTEGRITY, uC/OS, QNX, FreeBSD and OSE. Code is typically written in C or C++, but various high-level programming languages, such as Python and JavaScript, are now also in common use to target microcontrollers and embedded systems.Ada is used in some military and aviation projects.

...
Wikipedia