1. Based on level of complexity

(i) Small scale :

• Limited or simple hardware interface

• single running application

• low complexity

• no RTOS

eg. DC motor controller

(ii) Medium scale :

• Moderate no. of hardware interface

• simple primary application with multiple procedure/ISR

• Medium complexity

• No RTOS

eg. Digital clock

(iii) Sophisticated :

• High level or large number of hardware interface

• Fully multitasked

• High complexity

• RTOS

eg. Smartphones

2. Based on Time response :

System specific/finite time response and time deadlines are called as Real time embedded systems.

(i) Soft real-time E.S

• Deadlines are met statistically

eg. LCD or LED

(ii) Hard real time E.S

• Deadlines are met hard on each and every instance

eg. Nuclear reactor CS