A Microsoft Universal Printer Driver (aka Unidrv) "minidriver" for the Royal LetterMaster, a budget 1980s daisy wheel printer. It's supposed to run on Windows 2000 or later.
It doesn't work yet. Something about the .GPD file means it won't install, see: http://stackoverflow.com/questions/29633343/printer-installation-fails-with-unable-to-install-printer-some-driver-files-a
If you want to get this to work, you'll need to start Windows in the mode where it doesn't check driver signatures, because it's unsigned.
During development, the gpdcheck tool from the Windows Driver Kit is invaluable to check for syntax errors.
Add CatalogFile=LetterMaster.cat in the [Version] section of LetterMaster.inf.
To generate lettermaster.cat use Inf2Cat, available as part of the Windows Driver Kit. The command would look something like this:
inf2cat /drv:"F:\Projects\2015\Royal LetterMaster\LetterMaster-Unidrv" /os:2000,XP_X86,XP_X64,Server2003_X86,Server2003_IA64,Server2003_X64,Vista_X86,Vista_X64,Server2008_X86,Server2008_IA64,Server2008_X64,7_X86,7_X64,Server2008R2_IA64,Server2008R2_X64,Server8_x64,8_ARM,8_X86,8_X64,Server6_3_X64,6_3_ARM,6_3_X64,6_3_x86
Note that:
/drvis given the name of the directory containing the inf file, not the inf file itself/oshere is given every OS inf2cat supports, but there might be more in future
Then you'd need to sign it somehow to make this particularly meaningful.