My friend did his initial reading of C programming learning concepts fully. But want to practice this. If someone could suggest a mini project or idea for him to develop which would cover all major concepts of C programming it would be helpful.

There are lots of project one can try out to become good in the language learnt by them. To give you few examples are
1. To check out the concepts of structures, pointers, files, arrays one can try out any application programming like developing a student examination database system or a course scheduling system or library information system and so on.
2. To use the concepts of graphics programming extensively one can try out games programming like developing a chess program.
3. To use system calls one can try out building a small compiler which though would be in the advanced level.
Hope the above gives you idea for proceeding. Have a happy developing of project.