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Chainer

Chainer is intended for the multi-program version of dialogues, each module being one (or at least one) program. Chainer is a separate program that relies on receiving from its caller the name of the program module to be executed next. It is an attempt to allow for the fact that, since the individual .EXE files each contain a copy of all the library units, the modules of a single dialogue will often not fit onto one floppy disc; and helps guide the user to changing discs if the target module is not found on the current one.

This arrangement, however, has at least 2 major weaknesses:

Needs reliable inter-program communications.

No means of providing them has yet been found under DOS. Various means have been suggested, but even the most secure tends to rely on the adherence of other systems to conventions that are not officially documented.

Needs enough memory for both programs.

The DOS service it relies on needs to be able to load both caller and target program at the same time, which, without assurance of the availability of expanded memory, is a considerable demand.