No Indent Any More

[L. H. Huang]

Hi, buddies,

I changed some options of indentation in emacs, I don't remember what I 
did exactly. It mainly relates to the Group Editing and Programming -> C .
My problem is that there is no indent any more, after I press TAB key. 
The sentence I pressed TAB on will be moved to the left margin. After 
trying lots of ways, maybe made it even worse, I erased all of 
customization in Emacs. Unfortunately, it still doesn't work!
Who can tell me what I should? Thank you so much! BTW, I'm progromming 
in C/C++ with emacs.

Regards,

Linjia