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This might be a very stupid question.
I have experience with embedded software on bare-metal and just started with FREERTOS. However I don't really understand why one would use FREERTOS instead of the built in interrupt mechanism. The goal of multitasking is to give the impression some sort of parallellization is going on on a single core (similar to multithreading). If you have a main function that is running specific functions continuously, next to this you can have different interrupt routines with different importance levels that can interrupt that main function and then return to the main function. With an embedded OS you have some task running and it then gets interrupted to run a task with a higher priority.
So far in my eyes the final result seems pretty similar, could someone correct me and/or give some more explanation?