can some one tell me a prog of making different combinations using recursion in c/c++ and it should also be a function

Sounds like a homework question of some sort. And your question is somewhat unclear. Program to make diffrent combinations of what exactly. And yes it will be a function if it is recursive. Recursive functions make a call to "themselfs" until a condition is met. Here is a link to a sight with some great tutorials I would suggest you read through it. This page contains information on recursive functions.
Functions2

Give it a try yourself if you have problems with the code or questions after you have done some of your own research anyone here will be happy to help out.