General operating systems and Real time operating systems

 

An operating system act as mediator or channel between the computer users, computer hardware and application software. Operating system is used to provide friendly environment in which a computer user can run application softwares in a handy and efficient manner, alternately, operating system is software which manages the computer hardware. The role of an operating system is to provide resources and service allocation which includes input and output peripherals, memory, processors etc. (process management, main memory management, file system management, file management, I/O management, command management, network management, protection management)

 

Functions of Operating System

          Operating system performs three functions:

1.     Convenience: An operating system makes a computer more handy to use.

2.     Efficiency: An operating system permits the system resources of computer to be used in an efficient manner.

3. Ability to Evolve: An operating system must permit the effective development, testing and introduction of new system functions without major changes.

 

RTOS is an operating system that supports real time applications by providing logically correct result within the given time or deadline required. Basic Structure of real time operating system is similar to the general operating system but, additionally, it provides mechanisms to permit real time scheduling of tasks and will provide precise and predictable timing characteristics than general operating system. RTOS is the key  to most of the embedded systems and provides a platform to create applications. Embedded systems that are relatively simple, having less hardware does not require an real time operating systems (RTOS). Embedded systems having  more hardware and software applications needs scheduling of different tasks, and hence needs RTOS.

Key specifications of RTOS.

1.     Reliability: The RTOS must be reliable or trustable, i.e. it must be available for all time and must not fail to while performing any function or operation. The reliability of system equally depends on the hardware board support package and application code.

2.     Predictability: In RTOS, the user knows within what proportion period of time the RTOS goes to perform the task i.e. The RTOS has predictability. We can predict, determine what proportion time takes by RTOS.

3.     Performance: The performance of RTOS must be fast to fulfill the timing requirement of operations.

4.     Compactness: The RTOS must be compact so that it requires less memory space for storage and can be used for portable application, like cell phone, DVD players etc.

5.     Consistency: The consistency is the measure of performance. The RTOS must perform consistently.

 

Difference between General OS and RTOs

S.N.	General OS/ Desktop OS	RTOS (Real time OS)
1	No task deadline	Task deadline
2	Time response is not deterministic	Time response is deterministic
3	Not customizable	Customizable as per application
4	Does not optimize memory resources	Optimize memory resources
5	Stored in hard discs	Stored in semiconductor memories like EPROM
6	Used in universal applications	Used in specific applications
7	Ex. Windows, linux	Ex. Android, Vxworks