An operating system is a software that runs directly on the hardware.
It comes in between user software and hardware. The operating system is a combination of different software’s. Every software that operating system has to perform functions to manage the memory, processing time and complete utilization of resources without any deadlock situations.
At the very core of an operating system is a scheduler, which is guided by a Timer. The timer provides the regular interval for the scheduler to run. The job of the scheduler is to run various user program. It also monitors and controls the allocation of memory space to each user program.
An operating system can be classified as
- real-time
- single user
- multi-user
- multitasking
- multiprocessing
- general-purpose
Real-Time OS:
These are operating which respond to an event( internal or external) in a specified unit of time. If the system does not respond to the event in a specified unit of time; it corresponds to the failure of the system.
There are two major classifications of real-time os:
1. Hard Real-Time OS
2. Soft Real-Time OS
Hard Real-Time OS: These are the system which absolutely must respond to an event within a specified unit of time with the appropriate action. And that action is strictly governed and monitored. Failure of the OS in response time results in total system loss. Example: Network communication operating system running in mainframes to provide backbone infrastructure of voice-based communication such as PBX, POTS, Wireless Mobile Communication etc.
Soft Real-Time OS: These are also real-time operating but they are not so strict at hard real-time operating system. A missed event will not lead to a catastrophic loss. Example: General-pupose mobile devices operating system is soft real time operating system; in the event of incoming call the operating system may not respond to the user input and give priority to the incoming call notification from the modem.
Majorly embedded system have small memory and processing footprint. So to accommodate a ready made solution is very much out of the equation. You have to either heavily customize the operating system or make your own scheduler.
There are different real-time operating system provider
1. FreeRTOS
2. uC RTOS
3. mbed RTOS
4. CMSIS-RTOS
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