"Prem Patel" <23*7*2*1@s*u*e*t*u*a*e*u*a*> wrote: Firstly, remember that you need to submit 1 c source file. So, you need to merge these files together. The error you are getting usually mean you are trying to compile an object file. In other words a file with the ".o" extension. Object files are used when compiling multiple files together. If you want to compile two files together you need to "include" the other file in the main file. Usually the easiest way is to define a header file and then use a make file. However, you can't submit a header file or the second file or a make file so you need to merge the files together. This will fix the issue. I would describe how to compile two separate files, but I don't want people doing that since it goes against the requirement of the project. Just write one file to the other and compile a single file.