How do you code hardware support?

Actually, the best thing to do is to take advantage of the fact that DirectX has hardware support and use DirectX in your applications :) (Same applies to OpenGL)

That is what MAX is doing, it has a software renderer to ensure compatibility on all systems, but they also provide hardware accelerated DX and GL renderers.

This site has some good articles and tutorials for both APIs.

Coding an actual API type thing that has hardware acceleration is...difficult, to say the least. It requires a driver component to be functional, which means you'll either have to get a hold of the Windows DDK or develop for Linux.

After that, I have no idea [lol]

So programs like 3DS Max, Maya, and Photoshop are built off of DirectX or OpenGL?

Simple answer: forget it!

Like the others said, build something on top of Direct3D/OpenGL. Software Renderers are kinda very useless at the moment, but if you have some real complex calculations to make (which vertex/pixel shaders can't even do), THEN you need Software Renderers (which use ray-tracing to calculate each pixel's output).

In modern operating systems, you almost NEVER have DIRECT access (and I mean completely direct) to the hardware implementation.

Pretty much, it looks like this:

+-----------------+| THE HARDWARE    |+-----------------+|  OS  &  DRIVERS |+-----------------+|      APIs       |+-----------------+|    PROGRAMS     |+-----------------+

An old "operating system" that dosn't fit with this model is DOS. It looked similar to this:

+-----------------+|   HARDWARE      |+---------+       ||  OS     |       |+---------+-------+| APIs    |       |+---------+       ||    PROGRAM(S)   |+-----------------+

Although there were some APIs layering between the hardware and the program, they ended up being compiled into the progam itself. This is why many older DOS games have support for specific pieces of hardware ("soundblaster compatable").

Now, back to the modern world:

To access any piece of hardware, you use an API - or you write some assembly code, depending on wheither you're writing an application or a driver.

The two most popular 3D "low level" APIs (to which there are often drivers for each provided by a graphics card manufacturer) are OpenGL and DirectX.

One popular sound "low level" API is DirectSound.

Just a pair of examples.