Question regarding c programms with AST Gateway Interface

Hi all,
I am a new user and developer in Asterisk.I have executed some sample
programms of C thorough agi-bin.I want to have an Idea about what kind
of applications should be made in C for AGI.
If anyone can provide some link which has sample applications in c related to asterisk,
please tell me.
Thanks in Advance

Saurabh