...

[4wpL6Up4]

...

[salem c]

Your 2nd while (!input.eof()) never executes, because the first while (!input.eof()) reached end of file.

Put your if / else if code inside the first loop instead.

[4wpL6Up4]

...

[salem c]

You need ideas like
ofstream outupper("uppercase.txt");

and

outupper << data;

[salem c]

Great, another hit-and-run delete all the information poster.
Expect NO more help from me you selfish git.