application code for os independent

Question

I am writing C based embedded application code , I want to make it run in any OS which is written in 'C' like , free RTOS or Contiki or unix etc .

So I thought below are the module I need to create abstraction if I want to port easily on any of the os.

 1. Timer :  Callback  Timer,Event Timers 
 2. Network related(like  TCP send and receive)
 3. Mulitasking (STOP, RESUME, WAIT etc)

I am still thinking that there are other module which I need to abstract to port easily for other OS .. Can somebody suggest any other module?

Answer 1

1. File Access (Open, Close, Read, Write)
2. Sync (Locks, Mutexs and etc...)