DOS Fn 6521H: Upshift String

                                                         Compatibility: 3.3+ 
 Expects: AX    6521H
          CX    length of text, in bytes
          DS:DX address of text to convert
          ──────────────────────────────────────────────────────────────────
 Returns: AX    error code if CF is set to CY
          DS:DX the text is converted in place
          ──────────────────────────────────────────────────────────────────
    Info: Converts the specified number of characters starting at the
          address at DS:DX into uppercase, using the currently-active
          uppercase table for the active country and code page.

See Also: National Language Support
          DOS Functions
                                    -♦-