When I put #include <ctype.h> at the top of my source file, the compiler finds it. If I add #include <reg688.h>, I get error "can't open file 'reg688.h'". If change it to read #include <philips\reg688.h>, it still can't find the file. And if I put the full path in ( <c:\keil\c51\inc\philips\reg688.h> ) it STILL CAN'T FIND the file. What is this stupid compiler looking for?
I can recompile the original project and get the same executable file. But I don't want to change the original project or source files. So, I need to copy the source code to a new directory, create a new project file, and before I start modifying the code make sure I can build the original executable. This is not that difficult (or at least it shouldn't be), nor is it "the wrong way" to achieve my goal. We're talking about 8 source code files here. It's not like I'm trying to recreate building Windows.
And by the way, I did manage to recreate the original executable with my new project file. There was a code segment that the consultant created that had to be added manually to the project file that I was missing.
Don't worry about changing the project when you do the your job of extending the project.
You are expected to use source-code management, i.e. the changes you do will not destroy the original project. Instead, the source code manager will be able to restore either your version or the original version. And it will be able to show every difference between your new version and the original that the consultant left you with.
If you do not use source-code versioning, then it is time to stop all work and first think about how to work with source code. Any project that matters will require traceability, and that will require source-code management (and of course similar management of the requirements, test cases, bug tracker, ...)
But I don't want to change the original project or source files.
Then why are you doing it?
So, I need to copy the source code to a new directory, create a new project file,
Now, whatever gave you that strange idea? What does copying the project folder around have to do with creating a new project?
There was a code segment that the consultant created that had to be added manually to the project file that I was missing.
Aha. So the error was exactly where I told you to look, and that leads you to the conclusion that
nor is it "the wrong way" to achieve my goal
If the thought of ever buying a product based on such reasoning weren't so scary, that might even be funny.