Page 322 - DCAP103_Principle of operating system

Unit 10: Introduction of Windows and its Programming

Despite the fact that nearly all consumers and most businesses ignored NT 3.1 for desktop Notes
systems, it did acquire a small following in the server market. A few new 3.x releases with
small changes occurred in 1994 and 1995. These slowly began to acquire more following among
desktop users as well.
The first major upgradation to NT came with NT 4.0 in 1996. This system had the power, security,
and reliability of the new operating system, but also supported the same user interface as the
by then very popular Windows 95. This compatibility made it much easier for users to migrate
from Windows 95 to NT, and many of them did so.
From the beginning, NT was designed to be portable, so it was written almost entirely in C,
with only a tiny bit of assembly code for low-level functions such as interrupt handling. The
initial release consisted of 3.1 million lines of C for the operating system, libraries, and the
environment subsystems (discussed below). When NT 4.0 came out, the code base had grown
to 16 million lines of code, still mostly C, but with a small amount of C++ in the user interface
part. By this time the system was highly portable, with versions running on the Pentium, Alpha,
MIPS, and PowerPC, among other CPUs. Some of these have been dropped since then. The
story of how NT was developed is given in the site Showstopper. The site also tells a lot about
the key people involved.

Figure 10.1: Some Differences between Windows 98 and Windows NT

Item Windows 95/98 Windows NT

Full 32-bit system? No Yes
Security? No Yes

Protected file mappings? No Yes

Private addr space for each MS-DOS prog? No Yes
Unicode? No Yes
80x86, Alpha,
Runs on Intel 80x86
MIPS, …
Multiprocessor support? No Yes

Re-entrant code inside OS? No Yes

Plug and play? Yes No
Power management? Yes No

FAT-32 file system? Yes Optional

NTFS file system? No Yes
Win32 API? Yes Yes

Run all old MS-DOS programs? Yes No

Some critical OS data writable by user? Yes No

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