Sometimes you might have to modify a header (.h) file as well as a source file. To be sure that the modified header file is accessed by all source files in the program that include it, you must give as an argument to the fix command a list of all the source files that include that header file. If you do not include the list of source files, only the primary (current) source file is recompiled and only it includes the modified version of the header file. Other source files in the program continue to include the original version of that header file.