Software incompatibility

Software incompatibility is a characteristic of software components or systems which cannot operate satisfactorily together on the same computer, or on different computers linked by a computer network. They may be components or systems which are intended to operate cooperatively or independently. Software compatibility is a characteristic of software components or systems which can operate satisfactorily together on the same computer, or on different computers linked by a computer network. It is possible that some software components or systems may be compatible in one environment and incompatible in another.

Consider sequential programs of the form:

A particular program might use a printer (resource A) and a file (resource B) in order to print the file.

If several such programs P1,P2,P3 ... operate at the same time, then the first one to execute will block the others until the resources are released, and the programs will execute in turn. There will be no problem. It makes no difference whether a uni-processor or a multi-processor system is used, as it's the allocation of the resources which determines the order of execution.

Note, however, that programmers are, in general, not constrained to write programs in a particular way, or even if there are guidelines, then some may differ from the guidelines. A variant of the previous program may be:

The resources A and B are the same as in the previous example – not simply dummy variables, as otherwise the programs are identical.

As before, if there are several such programs, Q1,Q2,Q3 which run at the same time using resources as before, there will be no problem.

However, if several of the Ps are set to run at the same time as several of the Qs, then a deadlock condition can arise. Note that the deadlock need not arise, but may.

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