-- Embedded systems are more limited in hardware and/or software functionality than a personal computer (PC). This holds true for a significant subset of the embedded systems family of computer systems. In terms of hardware limitations, this can mean limitations in processing performance, power consumption, memory, hardware functionality, and so forth. In software, this typically means limitations relative to a PC-fewer applications, scaled-down applications, no operating system (OS) or a limited OS, or less abstraction-level code. However, this definition is only partially true today as boards and software typically found in PCs of past and present have been repackaged into more complex embedded system designs.
-- An embedded system is designed to perform a dedicated function. Most embedded devices are primarily designed for one specific function. However, we now see devices such as personal data assistant (PDA)/cell phone hybrids, which are embedded systems designed to be able to do a variety of primary functions. Also, the latest digital TVs include interactive applications that perform a wide variety of general unctions unrelated to the "TV" function but just as important, such as e-mail, web browsing, and games.
-- An embedded system is a computer system with higher quality and reliability requirements than other types of computer systems. Some families of embedded devices have a very high threshold of quality and reliability requirements. For example, if a car's engine controller crashes while driving on a busy freeway or a critical medical device malfunctions during surgery, very serious problems result. However, there are also embedded devices, such as TVs, games, and cell phones, in which a malfunction is an inconvenience but not usually a life-threatening situation.
-- Some devices that are called embedded systems, such as PDAs or web pads, are not really embedded systems. There is some discussion as to whether or not computer systems that meet some, but not all of the traditional embedded system definitions are actually embedded systems or something else. Some feel that the designation of these more complex designs, such as PDAs, as embedded systems is driven by nontechnical marketing and sales professionals, rather than engineers. In reality, embedded engineers are divided as to whether these designs are or are not embedded systems, even though currently these systems are often discussed as such among these same designers. Whether or not the traditional embedded definitions should continue to evolve, or a new field of computer systems be designated to include these more complex systems will ultimately be determined by others in the industry. For now, since there is no new industry-supported field of computer systems designated for designs that fall in between the traditional embedded system and the general-purpose PC systems.
Electronic devices in just about every engineering market segment are classified as embedded systems . In short, outside of being "types of computer systems," the only specific characterization that continues to hold true for the wide spectrum of embedded system devices is that there is no single definition reﬂecting them all.