What is an embedded system?

An embedded system is a special purpose system, in which the computer is encapsulated by the device it controls. Unlike a general purpose system an embedded system will only perform some particular tasks. These are actually systems which are developed for performing some predefined tasks. Embedded systems may vary from small hand held devices like PDAs to large devices like robotic arms.
Embedded systems are generally control systems which are a part of another device and they can handle the entire operation of that device. They are generally electronic chips with CPU, memory,I/o ports and are programmable.