Can we program the uC with "C" only ?

Hallo Yogesh,

answer on your question is: It depends. Sometimes there are timing critical routines, which should be coded in assembly, even if you are mainly coding in 'C'.

Please don't forget, that you need a deep understanding of your mcu, anyway how you code. You should know in detail, what timers do, or how instructions affect the flags, a.s.o.

If you want to proceed with 'C', don't forget, that it is not enough to learn 'C', but you must also learn, how your 'C'-compiler works. You must become familiar to it.

Bye,
Kai