Is it possible to do multitasking without context switch with just one cpu? All the article I can find seems to talk about multitasking and context switch as its a two different thing. It seems that multitasking and context switch are the same thing.
Yes, it is possible (depending upon what you mean by "context switch").  See cooperative multi-tasking.  In cooperative multi-tasking, the operating system never needs to perform a context switch between tasks -- instead, tasks voluntarily take care of saving their own state and switching between themselves.