What are the device drivers?
A device driver, or a software driver is a type of computer software, typically developed to make
the hardware in your computer work. Typically this constitutes an interface for communicating with
the device, through the specific computer bus or communications subsystem that the hardware is
connected to, providing commands to and/or receiving data from the device, and on the other end,
the
requisite interfaces to the operating system and software applications. Often called a driver for
short, it is a specialized hardware dependent computer program which is also operating system
specific that enables another program, typically an operating system or applications software
package or computer program running under the operating system kernel, to interact transparently
with a hardware device, and usually provides the requisite interrupt handling necessary for any
necessary asynchronous time-dependent hardware interfacing needs.
Device driver theory
The key design goal of device drivers is abstraction. Every model of hardware  even within the same
class of device  is different. Newer models also are released by manufacturers that provide more
reliable or better performance and these newer models are often controlled differently.
Computers and their operating systems cannot be expected to know how to control every device, both
now and in the future. To solve this problem, operating systems essentially dictate how every type
of device should be controlled. The function of the device driver is then to translate these OS
mandated function calls into device specific calls. In theory a new device, which is controlled in
a
new manner, should function correctly if a suitable driver is available. This new driver will
ensure
that the device appears to operate as usual from the operating systems  point of view.
Depending on the specific computer architecture, drivers can be 8-bit, 16-bit, 32-bit, and more
recently, 64-bit. This corresponds directly to the architecture of the operating system for which
those drivers were developed. For example, in 16-bit Windows 3.11, most drivers were 16-bits, while
most drivers for 32-bit Windows XP are 32-bit. More recently, specific 64-bit Linux and Windows
versions have required hardware vendors to provide newer 64-bit drivers for their devices.
Device driver development
Writing a device driver is considered a challenge in most cases, as it requires an in-depth
understanding of how a given platform functions, both at the hardware and the software level.
Because many device drivers execute in kernel mode, software bugs often have much more damaging
effects to the system. This is in contrast to most types of user-level software running under
modern
operating systems, which can be stopped without greatly affecting the rest of the system. Even
drivers executing in user mode can crash a system if the device being controlled is erroneously
programmed. These factors make it more difficult and dangerous to diagnose problems.
All of this means that the engineers most likely to write device drivers come from the companies
that develop the hardware. This is because they have more complete access to information about the
design of their hardware than most outsiders. Moreover, it was traditionally considered in the
hardware manufacturer s interest to guarantee that their clients would be able to use their
hardware
in an optimum way. However, in recent years non-vendors too have written numerous device drivers,
mainly for use under free operating systems. In such cases, co-operation on behalf of the vendor is
still important, however, as reverse engineering is much more difficult with hardware than it is
with software, meaning it may take a long time to learn to operate hardware that has an unknown
interface.
In Windows, Microsoft is attempting to address the issues of system instability by poorly written
device drivers by creating a new framework for driver development known as Windows Driver
Foundation
 WDF . This includes UMDF User Mode Driver Framework that encourages development of certain types
of
drivers - primarily those that implement a message-based protocol for communicating with their
devices - as user mode drivers. If such drivers malfunction they will not cause system instability.
The KMDF Kernel Mode Driver Framework model continues to allow development of kernel-mode device
drivers, but attempts to provide standard implementations of functions that are well known to cause
problems, including cancellation of I/O operations, power management, and plug and play device
support.
Device driver applications
Because of the diversity of modern hardware and operating systems, many ways exist in which drivers
can be used. Drivers are used for interfacing with:
Printers 
Video adapters 
Network cards 
Sound cards 
Local buses of various sorts - in particular, for bus mastering on modern systems 
Low-bandwidth I/O buses of various sorts  for pointing devices such as mice, keyboards, USB, etc. 

computer storage devices such as hard disk, CD-ROM and floppy disk buses  ATA, SATA, SCSI  
Implementing support for different file systems 
Implementing support for image scanners and digital cameras
Choosing and installing the correct device drivers for given hardware is often a key component of
computer system configuration.
Virtual device drivers
A particular variant of device drivers are virtual device drivers. They are used in virtualization
environments, for example when an MS-DOS program is run on a Microsoft Windows computer or when a
guest operating system is run inside e.g. VMware. Instead of enabling the guest operating system to
dialog with hardware, virtual device drivers take the opposite role and emulate a piece of
hardware,
so that the guest operating system and its drivers running inside a virtual machine can have the
illusion of accessing real hardware. Attempts by the guest operating system to access the hardware
are routed to the virtual device driver in the host operating system as e.g. function calls. 
The virtual device driver can also send simulated processor-level events like interrupts into the
virtual machine.
Note: DriverMax only works on Windows Vista, Windows XP and Windows 2003  all service packs .
Driver downloads are  only  available for Windows Vista and Windows XP users.