---

Before You Begin

You might have developed device drivers for other platforms—Mac OS 9, perhaps, or BSD or another flavor of UNIX. One thing you’ll discover reading this document is how different the approach is with the I/O Kit. Although writing drivers for Mac OS X requires new ways of thinking and different ways of programming, you are amply rewarded for shifting to this new approach. The I/O Kit simplifies driver development and supports many categories of devices. Once you get the basics of the I/O Kit down, you’ll find it a relatively easy and efficient matter to create device drivers.

Before you attempt driver development with the I/O Kit, Apple highly recommends certain prerequisites. Because the framework uses an object-oriented programming model, which is implemented in a restricted subset of C++, it helps to know C++ or object-oriented concepts in general. Also, device drivers are not the same thing as applications because, being kernel-resident, they must abide by more restrictive rules. Knowledge of kernel programming is therefore very useful.

Indeed, programming in the kernel is discouraged except when it is absolutely necessary. Many alternatives for communicating with hardware and networks exist at higher levels of the system, including the “device interface” feature of the I/O Kit described in “Controlling Devices From Outside the Kernel” See “Should You Program in the Kernel? ” for more on alternatives to kernel programming.

---