from normal byte to double byte programm

There are many.
- don't use type 'char' anywhere, use a custom-defined type like TCHAR in the windows codebase that you redefine to 16-bit.
- find all custom functions that deal with the 'char' and change them to this type
- make sure there areno assumptions anywhere about a character being one byte. For example, some places you may need to change a '1' to a 'sizeof(TCHAR)'
- make sure the correct system library string functions are being called (in windows if you define UNICODE it will use all the *W functions instead of the *A functions). You may not have this support onyour unix platform and may need to implement your own string functions or get a library

- be careful with strings passed to system library calls. For example, if your filenames are now stored as double byte, then you either need to call a double byte version of that system call, or you need to explicitly write a conversion function (double byte->single byte) to prepare filenames for each system librarycall (such as "rename" or "unlink"). If you were using C++ you could make this conversion implicit

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