ROM Hack C++ help?

[Lockon Stratos]

Which parts of C++ would I have to learn to be able to create editors for nds roms?

 

[nIxx]

You don´t even need C++ (every programming language works C,Python,C# or whatever) basically you will need to read the file and interpret the data the right way.
But first you should start here Romhacking

 

[DarthNemesis]

String manipulation, arrays, input/output streams, bit shifting, casting, pointers, MFC/Win32 API...

But I told you, you really should start with C#. It has native Unicode support, no memory management to worry about, more type safety, and easier GUI design.

 

[SCVgeo]

Which parts of C++ would I have to learn to be able to create editors for nds roms?

Is there any particular reason you want to do it in C++? Do you know any C++ already?

If not then you should use C#. If you do, you should probably still use C#. Unless there is a good reason for using C++ instead.