appearance of the KL-10 (one model of the PDP-10), none of whose connectors matched anything else] n. The tendency of manufacturers (or, by extension, programmers or purveyors of anything) to come up with new products that don't fit together with the old stuff, thereby making you buy either all new stuff or expensive interface devices. The KL-10 Massbus connector was actually *patented* by DEC, which reputedly refused to license the design and thus effectively locked third parties out of competition for the lucrative Massbus peripherals market. This policy is a source of never-ending frustration for the diehards who maintain older PDP-10 or VAX systems. Their CPUs work fine, but they are stuck with dying, obsolescent disk and tape drives with low capacity and high power requirements.(A closely related phenomenon, with a slightly different intent, is the habit manufacturers have of inventing new screw heads so that only Designated Persons, possessing the magic screwdrivers, can remove covers and make repairs or install options. Older Apple Macintoshes took this one step further, requiring not only a hex wrench but a specialized case-cracking tool to open the box.)
In these latter days of open-systems computing this term has fallen somewhat into disuse, to be replaced by the observation that "Standards are great! There are so *many* of them to choose from!" Compare backward combatability.