DIRECT EXPLAINED

DirectX explained
Ever wondered just what that enigmatic name means?

Gaming and multimedia applications are some of the most satisfying
programs you can get for your PC, but getting them to run properly isn’t
always as easy as it could be. First, the PC architecture was never
designed as a gaming platform. Second, the wide-ranging nature of the PC
means that one person’s machine can be different from another. While
games consoles all contain the same hardware, PCs don’t: the massive
range of difference can make gaming a headache.

  To alleviate as much of the pain as possible, Microsoft needed to
introduce a common standard which all games and multimedia applications
could follow – a common interface between the OS and whatever hardware
is installed in the PC, if you like. This common interface is DirectX,
something which can be the source of much confusion.

  DirectX is an interface designed to make certain programming tasks
much easier, for both the game developer and the rest of us who just
want to sit down and play the latest blockbuster. Before we can explain
what DirectX is and how it works though, we need a little history
lesson.

DirectX history

Any game needs to perform certain tasks again and again. It needs to
watch for your input from mouse, joystick or keyboard, and it needs to
be able to display screen images and play sounds or music. That’s pretty
much any game at the most simplistic level.

  Imagine how incredibly complex this was for programmers developing
on the early pre-Windows PC architecture, then. Each programmer needed
to develop their own way of reading the keyboard or detecting whether a
joystick was even attached, let alone being used to play the game.
Specific routines were needed even to display the simplest of images on
the screen or play a simple sound.

  Essentially, the game programmers were talking directly to your
PC’s hardware at a fundamental level. When Microsoft introduced Windows,
it was imperative for the stability and success of the PC platform that
things were made easier for both the developer and the player. After
all, who would bother writing games for a machine when they had to
reinvent the wheel every time they began work on a new game? Microsoft’s
idea was simple: stop programmers talking directly to the hardware, and
build a common toolkit which they could use instead. DirectX was born.

How it works

At the most basic level, DirectX is an interface between the hardware
in your PC and Windows itself, part of the Windows API or Application
Programming Interface. Let’s look at a practical example. When a game
developer wants to play a sound file, it’s simply a case of using the
correct library function. When the game runs, this calls the DirectX
API, which in turn plays the sound file. The developer doesn’t need to
know what type of sound card he’s dealing with, what it’s capable of, or
how to talk to it. Microsoft has provided DirectX, and the sound card
manufacturer has provided a DirectX-capable driver. He asks for the
sound to be played, and it is – whichever machine it runs on.

From our point of view as gamers, DirectX also makes things
incredibly easy – at least in theory. You install a new sound card in
place of your old one, and it comes with a DirectX driver. Next time you
play your favourite game you can still hear sounds and music, and you
haven’t had to make any complex configuration changes.

Originally, DirectX began life as a simple toolkit: early hardware
was limited and only the most basic graphical functions were required.
As hardware and software has evolved in complexity, so has DirectX. It’s
now much more than a graphical toolkit, and the term has come to
encompass a massive selection of routines which deal with all sorts of
hardware communication. For example, the DirectInput routines can deal
with all sorts of input devices, from simple two-button mice to complex
flight joysticks. Other parts include DirectSound for audio devices and
DirectPlay provides a toolkit for online or multiplayer gaming.

DirectX versions

The current version of DirectX at time of writing is DirectX 9.0.
This runs on all versions of Windows from Windows 98 up to and including
Windows Server 2003 along with every revision in between. It doesn’t
run on Windows 95 though: if you have a machine with Windows 95
installed, you’re stuck with the older and less capable 8.0a. Windows NT
4 also requires a specific version – in this case, it’s DirectX 3.0a.

With so many versions of DirectX available over the years, it becomes
difficult to keep track of which version you need. In all but the most
rare cases, all versions of DirectX are backwardly compatible – games
which say they require DirectX 7 will happily run with more recent
versions, but not with older copies. Many current titles explicitly
state that they require DirectX 9, and won’t run without the latest
version installed. This is because they make use of new features
introduced with this version, although it has been known for lazy
developers to specify the very latest version as a requirement when the
game in question doesn’t use any of the new enhancements. Generally
speaking though, if a title is version locked like this, you will need
to upgrade before you can play. Improvements to the core DirectX code
mean you may even see improvements in many titles when you upgrade to
the latest build of DirectX. Downloading and installing DirectX need not
be complex, either.

Upgrading DirectX

All available versions of Windows come with DirectX in one form or
another as a core system component which cannot be removed, so you
should always have at least a basic implementation of the system
installed on your PC. However, many new games require the very latest
version before they work properly, or even at all.

Generally, the best place to install the latest version of DirectX
from is the dedicated section of the Microsoft Web site, which is found
at www.microsoft.com/windows/directx.
As we went to press, the most recent build available for general
download was DirectX 9.0b. You can download either a simple installer
which will in turn download the components your system requires as it
installs, or download the complete distribution package in one go for
later offline installation.

Another good source for DirectX is games themselves. If a game
requires a specific version, it’ll be on the installation CD and may
even be installed automatically by the game’s installer itself. You
won’t find it on magazine cover discs though, thanks to Microsoft’s
licensing terms.

Diagnosing problems

Diagnosing problems with a DirectX installation can be problematic,
especially if you don’t know which one of the many components is causing
your newly purchased game to fall over. Thankfully, Microsoft provides a
useful utility called the DirectX Diagnostic Tool, although this isn’t
made obvious. You won’t find this tool in the Start Menu with any
version of Windows, and each tends to install it in a different place.

The easiest way to use it is to open the Start Menu’s Run dialog,
type in dxdiag and then click OK. When the application first loads, it
takes a few seconds to interrogate your DirectX installation and find
any problems. First, the DirectX Files tab displays version information
on each one of the files your installation uses. The Notes section at
the bottom is worth checking, as missing or corrupted files will be
flagged here.

The tabs marked Display, Sound, Music, Input and Network all relate
to specific areas of DirectX, and all but the Input tab provide tools to
test the correct functioning on your hardware. Finally, the More Help
tab provides a useful way to start the DirectX Troubleshooter,
Microsoft’s simple linear problem solving tool for many common DirectX
issues.