any one plz tell me the basics of sending AT commands to microcontroller from GSM kit
I can see the doubts.
You normally send the AT commands _from_ the microcontroller and _to_ the GSM kit. Not the reverse.
Obviously, you need to consider the electrical interfaces - how to connect the microcontroller with the GSM kit. That will require you to read the datasheet for the microcontroller and corresponding documentation for the GSM kit.
Then you use your knowledge about programming a microcontroller to send AT commands using the used interface.
Quite easy.
But exactly what part of your school work have you done? Or did you go directly to the net to ask questions?
Why do you title this "doubts"?
What have you heard and/or read that you doubt? What is it, exactly, that you doubt about it?
The basics of AT Commands have absolutely nothing whatsoever to do with microcontrollers or programming.
The basics of AT Commands involve:
1. Understanding what AT Commands your particular "GSM Kit" supports;
2. Choosing which of those commands will be necessary to support your intended application;
3. Understanding what responses to expect when you send these commands to the "GSM Kit" - including error and/or failure indications.
Again, none of that has anything to do with microcontrollers or programming - it just requires you to study the documentation for your "GSM Kit", and to think.
As an aid to your study & thinking, you could try:
A. googling - there is loads of information available on this!
B. sending commands "manually" and observing the responses - eg, using hyperterminal.