O extension is related to Compiled Object Files. You have chance to open o files with C compiler.
O extension files are produced by C compiler. You have chance to create various softwares with c programming language. To create exe files by using o extension files, you may need c compiler. If you need to learn more, please check the following web pages.
What to use o
which page related to o file
o Related Searches
You can check related links about o fileextension.