Many of the insights for capabilities appear in language design. It is hard to determine whether they arose first in language design or OS design. Perhaps that is not important. The B5500 had hardware that was described as directly supporting the scope rules of Algol 60. It is also reminiscent of modern memory mapping hardware. In any case there are important ideas in each camp that are needed in the other.

The most widely known language now is perhaps C which provides nested scopes wherein defined names are protected from reference outside the scope. This scheme was present in the earliest programming languages and indeed was present in earlier mathematical languages such as Church's Lambda Calculus.

See other notes on Language ideas.