Operating system Books PDF:
1. https://www.tutorialspoint.com/operating_system/operating_system_tut
     orial.pdf
  2. NPTEl http://nptel.ac.in/downloads/106108101/
  3. http://www.cs.utexas.edu/users/witchel/372/lectures/01.OSHistory.pdf
    Real time system
    LIU BBOK http://www.cse.hcmut.edu.vn/~thai/books/2000%20_%20Liu-
    %20Real%20Time%20Systems.pdf
    Video Lecture NPTEL http://nptel.ac.in/courses/106105036/
    Software Engineering
    1. NPTEL PDF Unit
    http://nptel.ac.in/downloads/106105087/
    2. NPTEL video lecture
       http://www.nptelvideos.in/2012/11/software-engineering.html