"Error Handling can be used beyond the three mentioned above. For example, the ENOENT error code corresponds to “No such file or directory” and EACCES corresponds to a “Permission denied” error. In our own code we could communicate errors to calling functions by setting the errno variable, however, we may run into compatibility issues with the standard error codes or POSIX error codes. Instead, it may be more appropriate to do error handling by utilizing the return value of a function to communicate an error code. We could design our functions to always return an int value to indicate an error: 0 for no error and some non-zero value to indicate various different types of errors. Of course, as a consequence any value that needs to be “returned” to the calling function would need to be done so via a pass by reference variable."