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Inter-Program Memory

This version of PCVideo does not attempt to provide inter-program storage.

Under the p-System, the Intel-family interrupt vector list, residing in the first 1K of memory, is used only by the BIOS and is never altered by running applications. None of the rest of the system has any need of it. PCVideo therefore takes advantage of various vectors, known to be unused by the BIOS, to provide storage of values in memory between programs.

Under DOS, however, the interrupt vector list is the central multiplexor of all system functions, and is liberally used by the BIOS, by DOS itself, by DOS shells and extenders, and by many applications. However, allocation of various regions of vectors to these different types of usage is mostly undocumented. Though a certain degree of convention has evolved to guide a given package's choice of vector, there appears to be no security that a given vector, believed to be unused by convention, will not unexpectedly be used by some other software package used by a dialogue user in the same system as the dialogue.