Compatibility: 3.3+
Expects: AX    6522H
DS:DX address of ASCIIZ  string to upshift
                                                                  
Returns: AX    error code if CF is set to CY
DS:DX the string is converted in place
                                                                  
Info: Converts all of the characters of the ASCIIZ string starting at
DS:DX into uppercase, using the currently-active uppercase table
for the active country and code page.

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DOS Fn 6522H: Upshift ASCIIZ String