What programming model first released in 1991 can be used to write applications for the OPOS API?
OPOS: OPOS, full name OLE for Retail POS, a platform specific implementation of UnifiedPOS, is a point of sale device standard for Microsoft Windows operating systems that was initiated by Microsoft, NCR, Epson, and Fujitsu-ICL and is managed by the Association for Retail Technology Standards. OPOS:  The standard uses component object model and, because of that, all languages that support COM controls (i.e. Visual C++, Visual Basic, and C#) can be used to write applications.
i don't know