Features of Embedded Systems

1) Single-functioned System

• Most of the embedded system usually executes a single job repetitively.
    Example: 

a) A washing machine has an embedded controller that can take user inputs regarding knob settings and perform the washing job.
b) A pager is used to send messages.
c) A cell phone is used to establish communication between two persons.

2) Interaction with the physical environment

• Most of the embedded systems interact with the physical environment around them.
• Data are collected from the environment using sensors while actuators are used to control some of the parameters of the environment.

3) User interface

• Unlike the common user interfaces like keyboard, mouse, screen, etc. in general computing systems, embedded systems often contain dedicated user interfaces consisting of Push Buttons, LEDs, Steering Wheels, etc.

4) Dependable Systems

• Embedded Systems are often used in safety-critical applications, like nuclear power plants, medical instruments, etc. This necessitates a high level of reliance on such systems.
• Embedded systems often work in autonomous mode, interacting with the environment and impacting upon it directly.
• Apart from system reliability, a dependable system must ensure easy maintainability, good availability, a high degree of environmental safety and security of the information it processes.

5) Tightly Constrained System

• All computing systems have constraints on design metrics, but those on embedded systems can be especially tight. A design metric is a measure of an implementation’s features, such as cost, size, performance, and power.
• Embedded systems should be a low-cost solution to the problem so that the overall system is cheap, must be sized to fit on a single chip, must perform fast enough to process data in real-time, and must consume minimum power to extend battery life or prevent the necessity of a cooling fan.

6) Real-time System

• Most embedded systems are real-time in nature. They have a limited and set length of time to respond to a request from the environment.

Failing to do so could result in a dire circumstances.

• Example: Failure to activate fire extinguishers immediately after getting a fire alarm through sensors, may destroy the entire plant.
• Based on the above fact, Real-time systems are classified into two categories

a) Hard Real-Time Systems

b) Soft Real-Time Systems

7) Reactive System

• Reactive systems have continual interaction with the environment.
• The behavior of the system is very much dependent on the events occurring in the environment.
• This type of system normally has a set of states. Depending upon the occurrence of events, state transitions in the procedure take place.

8) Hybrid System

• Many of the real-time systems are hybrid in nature, as they include both analog and digital components.