graphical API was changed to such a degree that it proved difficult for software manufacturers to support both
platforms.
By September 1990, conflicts between IBM and Microsoft reached a peak and required that the two companies go
their separate ways. IBM took over OS/2 and Microsoft made it clear that Windows was the center of their strategy
for operating systems. While OS/2 still has some fervent admirers, it has not nearly approached the popularity of
Windows.
Microsoft Windows version 3.1 was released in April 1992. Several significant features included the TrueType font
technology (which brought scaleable outline fonts to Windows), multimedia (sound and music), Object Linking and
Embedding (OLE), and standardized common dialog boxes. Windows 3.1 ran only in protected mode and required
a 286 or 386 processor with at least 1 MB of memory.
Windows NT, introduced in July 1993, was the first version of Windows to support the 32-bit mode of the Intel
386, 486, and Pentium microprocessors. Programs that run under Windows NT have access to a 32-bit flat address
space and use a 32-bit instruction set. (I'll have more to say about address spaces a little later in this chapter.)
Windows NT was also designed to be portable to non-Intel processors, and it runs on several RISC-based
workstations.
Windows 95 was introduced in August 1995. Like Windows NT, Windows 95 also supported the 32-bit
programming mode of the Intel 386 and later microprocessors. Although it lacked some of the features of Windows
NT, such as high security and portability to RISC machines, Windows 95 had the advantage of requiring fewer
hardware resources.
Windows 98 was released in June 1998 and has a number of enhancements, including performance improvements,
better hardware support, and a closer integration with the Internet and the World Wide Web.
Aspects of Windows
Both Windows 98 and Windows NT are 32-bit preemptive multitasking and multithreading graphical operating
systems. Windows possesses a graphical user interface (GUI), sometimes also called a "visual interface" or "graphical
windowing environment." The concepts behind the GUI date from the mid-1970s with the work done at the Xerox
PARC for machines such as the Alto and the Star and for environments such as SmallTalk. This work was later
brought into the mainstream and popularized by Apple Computer and Microsoft. Although somewhat controversial
for a while, it is now quite obvious that the GUI is (in the words of Microsoft's Charles Simonyi) the single most
important "grand consensus" of the personal-computer industry.
All GUIs make use of graphics on a bitmapped video display. Graphics provides better utilization of screen real
estate, a visually rich environment for conveying information, and the possibility of a WYSIWYG (what you see is
what you get) video display of graphics and formatted text prepared for a printed document.
In earlier days, the video display was used solely to echo text that the user typed using the keyboard. In a graphical
user interface, the video display itself becomes a source of user input. The video display shows various graphical
objects in the form of icons and input devices such as buttons and scroll bars. Using the keyboard (or, more directly,
a pointing device such as a mouse), the user can directly manipulate these objects on the screen. Graphics objects
can be dragged, buttons can be pushed, and scroll bars can be scrolled.
The interaction between the user and a program thus becomes more intimate. Rather than the one-way cycle of
information from the keyboard to the program to the video display, the user directly interacts with the objects on the
display.
Users no longer expect to spend long periods of time learning how to use the computer or mastering a new program.
Windows helps because all applications have the same fundamental look and feel. The program occupies a window
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