UNIT - I Introduction : Introduction to UNIX/LINUX, Overview of Commands, File I/O, (open, create, close, Iseek, read, write),Process Control (fork, vfork, exit, wait, waitpid, exec). (Chapter - 1) UNIT - II Real Time Operating Systems : Brief History of OS, Defining RTOS, The Scheduler, Objects, Services, Characteristics of RTOS, defining a Task, Tasks States and Scheduling, Task Operations, Structure, Synchronization, Communication and Concurrency. Defining Semaphores, Operations and Use, Defining Message Queue, States, Content, Storage, Operations and Use . (Chapter - 2) UNIT - III Objects, Services and I/O : Pipes, Event Registers, Signals, Other Building Blocks, Component Configuration, Basic I/O Concepts, I/O Subsystem. (Chapter - 3) UNIT - IV Exceptions, Interrupts and Timers : Exceptions, Interrupts, Applications, Processing of Exceptions and Spurious Interrupts, Real Time Clocks, Programmable Timers, Timer Interrupt Service Routines (ISR), Soft Timers, Operations. (Chapter - 4) UNIT - V Case Studies of RTOS : RT Linux, MicroC/OS-II, Vx Works, Embedded Linux, and Tiny OS. (Chapter - 5)