Overview

When writing a program for the BeOS, as opposed to porting a program to the BeOS, you have two styles to choose from. One is the POSIX style, which resembles the UNIX environment, and the other is the object-oriented BeOS API (application programming interface). As porters of mostly UNIX software, we are more interested in the POSIX compatibility layer. Before we take a closer look at the POSIX support provided by the BeOS, we will take a brief look at both styles, how the two can be used together, where the differences and similarities are apparent, and where the two styles cross over.

16.1 Program Styles

If you take a look at the diagram of how the BeOS works in Figure 16-1, you can see how the two programming interfaces interlock with each other. The BeOS API attaches itself directly to the kernel, as does the POSIX support. You will also notice that the BeOS API covers some of the POSIX support and, in some cases, is actually built on the POSIX functions.

This is a fairly simplistic representation; the entire application support is slightly more complex and sophisticated. We can, however, make some analogies between the BeOS and other OSs. We already know there are two different styles of programs within the BeOS: those based on the BeOS API and those based on the POSIX-style interface.

The main difference between the two styles from the user's point of view is the interface that will be used. A BeOS...