Microsoft Word Hardware Reconfiguration Methodology V final2

System dependencies

1. Interdependencies

Every operating system has interdependencies. Interdependency exists where one or more software components rely on other components. These components can be either related (part of the same application) or completely unrelated (from a different application). Related or not, there is nevertheless a relationship between the various components. In this relationship, one component requires something from the other. It could also be that both components are co- dependent (dependent on each other) or the dependency could be one-way only. Most often, it is

functions and API’s that are required by one component from another. However, depending on how the software was written (including the overall design) co-dependent components do exist where they require one another for their own proper functioning.

To better understand interdependency, it helps to use a simple example. For instance, the example of an application and software library come easily to mind. In order for the application to work correctly, it requires access to certain functions and API’s that can only be satisfied by that specific library. Otherwise, the programmer will have to recreate those functions and API’s; this is a very complex and time-consuming process. However, often time the software library is not actually a part of the application; instead, it is from a different application altogether (this is particularly common in UNIX). However, because the programmer wishes to reduce the amount and complexity of his work, using functions and API’s developed by others reduces his time, work, and expended effort. Programmers tend to prefer building on pre-existing work (i.e. functions, API’s, system calls) since doing otherwise can lead to increased programming and operating system complexity.

In large Linux-based operating systems, it is common to have many thousands of such interdependencies. Such a system could have thousands of applications installed and most of them will require functions and API’s from any one of the various software libraries found distributed across the operating system. Although it is possible to develop entirely self-contained applications, it is normally not done, as rewriting existing library functionality already available is unproductive.

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