Embedded system is a special computer system, as a part of device or equipment. Generally, an embedded system is an embedded processor control board whose control program is stored in ROM. In fact, all devices with digital interfaces, such as watches, microwave ovens, video recorders, automobiles, etc., use embedded systems. Some embedded systems also include operating systems, but most embedded systems use a single program to realize the whole control logic. 
Defined from the application object, embedded system is a combination of software and hardware, and can also cover machinery and other ancillary devices. The widely recognized definition of embedded system in China is: a special computer system that takes application as the center, takes computer technology as the foundation, has tailorable software and hardware, and meets the strict requirements of application system on function, reliability, cost, volume, power consumption and so on.
An embedded system device is generally composed of an embedded computer system and an execution device,
Embedded computer system is the core of the whole embedded system, which is composed of hardware layer, middle layer, system software layer and application software layer. The execution device, also known as the controlled object, can accept the control commands sent by the embedded computer system and perform the specified operations or tasks. The execution device can be very simple, such as a micro motor on the mobile phone, which turns on when the mobile phone is in the vibration receiving state; It can also be complex, such as Sony intelligent robot dog, which integrates multiple micro control motors and a variety of sensors, so that it can perform various complex actions and feel various state information.