I want to know how to open vi editor or emacs editor in ubuntu 12.04

https://help.ubuntu.com/community/VimHowto
https://help.ubuntu.com/community/EmacsHowto

What do you mean by run "c" program?

In order to run a c program you first need to compile it

Step 1: Open a terminal

If you are using the Gnome interface, open the Terminal console via "Applications->Accessories->Terminal"

If you are using the Unity interface, the easiest way to open the Terminal is to use the 'search' function on the dash. Or you can click on the 'More Apps' button, click on the 'See more results' by the installed section, and find it in that list of applications. A third way, available after you click on the 'More Apps' button, is to go to the search bar, and see that the far right end of it says 'All Applications'. You then click on that, and you'll see the full list. Then you can go to Accessories > Terminal after that.

So the methods in Unity are:
Dash > Search for Terminal
Dash > More Apps > 'See More Results' > Terminal
Dash > More Apps > Accessories > Terminal

Step 2: enter the following command

gcc

If you see something similar to this

warren@wmh-lt:~$ gcc
gcc: fatal error: no input files
compilation terminated.
warren@wmh-lt:~$

Then you have the tools installed if you get an error message that gcc is not found then you will need install them

the command for this is

sudo apt-get install build-essential

once its installed you can complie the program and run it.

There are many tutorials around on both gcc and c programming. Google is your friend here have a good search

Please read the useful http://ubuntu-manual.org/