Types of RTOS

Types of RTOS


Two thoughts of mind when it comes to a RTOS

1.Hard real time operating system
2.Soft real time operating system

--Those that have critical time constraint and those that have softer time constraint
--Both perform same functions, but different in fashions

Hard RTOS

--Required to complete a critical task within a guaranteed amount of time.
--A process is submited along with the time necessary to complete its operations
--The scheduler then does one of two operations :
- The first would be the allowance of the process, guaranteeing that the process will be completed on time
-The second would be the rejection of the process. This is known as resource reservation. This type of guarantee requires that the scheduler knows the exact length of time each type of process the operating system to perform
--Therefore, each operation must be guaranteed to take an optimal amount of time.
--“Hard real time system are composed of special purpose software running on hardware dedicated to their critical process"

Example :

NASA space shuttles

--Often thought to be the most complicated and critical systems designed today
--On top of critical task requirement, there are interactions with literally thousand of devices and are backed up with redundant system

Soft RTOS

--Less restrictive time by nature
--Requires that critical processes receive priority over less critical ones.
--Implementation of soft real time applications requires careful design of the scheduler and other related aspect of the operating system
--System interactions must be known as well as the system must have priority scheduling giving the highest priority ti real time processes
--In addition, the dispatch latency must be small

Example

-Simple remote control
-Blender or toaster
-Teletype phone
-PDA, mobile phone, pager etc