Processing files within a directory one by one

Hi

How to create a shell script which takes in to account all the files present within a directory DIR one by one
e.g.

suppose i have a directory named DIR where there are files with the extension .ABC

i want to create shell script which processes all these files one by one.

please provide the code of the shell script?

thanks

Please use the search before posting. This would have easily been answered by either searching this site or by using an internet search engine.