The CCompilerDriver package lets you work with C compilers that are installed on your computer. It is used automatically by the Wolfram System compiler when you set the option CompilationTarget to "C", but you can use it to build your own executables, libraries, and object files from source code written in the C language.
If the input came from one or more files of C code, these could be given to CreateObjectFile in a list.
CreateObjectFile lets you compile different source files with different settings.
More information on options and settings is found in the section on Configuring the Compilation.