The key distinction is programmability and general-purpose function: devices designed solely or principally to perform arithmetic or fixed mathematical operations classify here, while machines capable of storing and executing user-defined programs typically fall under ADP headings. When a device straddles both functions, the principal-use test and the machine's marketed purpose guide classification.

Both printing and display-only calculating machines can fall under 75122 provided they are not more specifically classifiable elsewhere. The presence of a printing mechanism alone does not shift classification, but if the device also performs copying or facsimile functions it may instead belong under a multifunction office machine heading.