Chapter 8 Standard Application Interfaces and POSIX Interfaces

This chapter describes the changes made to the API organization in version 5.0 of the ChorusOS operating system.

API Reorganization

A major enhancement in ChorusOS 5.0 is the provision of a POSIX API. This new POSIX API provides complete support for POSIX processes, allowing application developers to to port POSIX-compliant applications directly to ChorusOS systems.

The ChorusOS microkernel API, available in previous versions of the product, is still supported, allowing you to use microkernel API calls directly. The ChorusOS microkernel API is provided to:

• Provide more efficient access to the microkernel primitive, when real-time operating is essential.

• Allow compatibility with applications developed for earlier versions of the ChorusOS system.

This new API organisation requires that you choose to develop your applications using only one of the ChorusOS APIs:

• ChorusOS POSIX API

• ChorusOS microkernel API

The different APIs represent two different development environments and you will develop your applications on one OR the other. You are strongly encouraged to use the ChorusOS POSIX API, as this offers maximum flexibility and allows you to port POSIX applications easily. A ChorusOS POSIX application cannot access the ChorusOS microkernel API, however. If you specifically need to emphasize performance issues, or if you need to access the microkernel primitives directly, you will need to use the ChorusOS microkernel API.

It is not possible to use both the ChorusOS POSIX API and the ChorusOS microkernel API in a single application, although there are a few exceptions to this rule.

For a complete description of the API reorganization and the rules governing the new API organization, refer to "Introduction to ChorusOS Applications" in the ChorusOS 5.0 Application Developer's Guide and to the API(5FEA) man page.