Hardware Reference
In-Depth Information
The only major changes to the file system were the addition of long file names in
place of the8+3character file names allowed in
MS-DOS
and the ability to have
more than 65,536 blocks on a disk.
Even with the release of Windows 98 in 1998,
MS-DOS
was still there (now
called version 7.1) and running 16-bit code. Although a bit more functionality
migrated from the
MS-DOS
part to the Windows part, and a disk layout suitable for
larger disks was now standard, under the hood, Windows 98 was not very different
from Windows 95. The main difference was the user interface, which integrated
the desktop, the Internet, and to some extent, even television more closely. It was
precisely this integration that attracted the attention of the U.S. Dept. of Justice,
which then sued Microsoft claiming that it was an illegal monopoly. Windows 98
was followed by the short-lived Windows Millennium Edition (ME), which was a
slightly improved Windows 98.
While all these developments were going on, Microsoft was also busy with a
completely new 32-bit operating system being written from the ground up. This
new system was called
Windows New Technology
,or
Windows NT
. It was ini-
tially hyped as the replacement for all other operating systems for Intel-based PCs
(as well as the MIPS PowerPC chips), but it was somewhat slow to catch on and
was later redirected to the upper end of the market, where it found a niche on large
servers. The second version of NT was called Windows 2000 and became the
mainstream version, also for the desktop market. The successor to Windows 2000
was Windows XP, but the changes here were relatively minor (better backward
compatibility and a few more features). In 2007, the followup Windows Vista was
released. Vista implemented many graphical enhancements over Windows XP, and
it added many new user applications, such as a media center. Vista's adoption was
slow because of its poor performance and high resource demands. A mere two
years later, Windows 7 was released, which by all accounts is a tuned-up version of
Windows Vista. Windows 7 runs much better on older hardware, and it requires
significantly less hardware resources.
Windows 7 is sold in six different versions. Three are for home users in vari-
ous countries, two are aimed at business users, and one combines all the features of
all versions. These versions are nearly identical and differ primarily in focus, ad-
vanced features, and optimizations made. We will focus on the core features and
not make any further distinction between these versions.
Before getting into the interface Windows 7 presents to programmers, let us
take a very quick look at its internal structure, which is illustrated in Fig. 6-32. It
consists of a number of modules that are structured in layers and work together to
implement the operating system. Each module has some particular function and a
well-defined interface to the other modules. Nearly all the modules are written in
C, although part of the graphics device interface is written in C++ and tiny bits of
the lowest layers are written in assembly language.
At the bottom is a thin layer called the
hardware abstraction layer
. Its job is
to present the rest of the operating system with abstract hardware devices, devoid
