The complexity of applications can be reduced drastically by breaking it down into several tasks. The tasks can be designed so that they are dedicated to some external peripheral, internal data structure etc.
For example, a task may be dedicated to running the IIC bus. Another may be dedicated to a modem connected to the serial port.etc.etc.
This is where the OS comes into the picture.
It provides, to the tasks, the CPU and other resources like timers, ports etc in a controlled manner. This is multitasking. But this is not enough.
The OS also provides messaging facility so that the tasks can communicate with each other. This allows you to do powerful things with simple tasks.

Infact, with an OS the application development part should be approached in a totally different manner.

If you are unable to visualise tasks in such a manner, you should not belittle OS-on-micro concept.


Rumi