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Application libraries
in the system
As time passed, operating system
designers began to add more and more abstractions to handle file management,
printing, graphics, and other programming tasks. Programmers in turn began to
create more complex applications that took advantage of these capabilities and
added new ones. In the 1980s, as shown in the middle of Figure 1, system software
such as Mac OS, Windows, and OS/2© expanded to include application libraries
that developers could use to add new capabilities to their applications,
including menus, windows, dialog boxes, networking, telecommunications,
interapplication communication, and so on.
For example, a Mac OS programmer needs to call just one function to display a
standard dialog box that allows users to scroll through lists of files,
directories, and disk drives; responds appropriately when the user clicks or
double-clicks various fields and buttons within the dialog box; and returns
control to the application only after the user has made an appropriate selection.
Although some tasks may require calling lower-level operating system functions
directly, in general the applications written for this kind of system software
include more calls to application libraries than to the underlying operating
system libraries.
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Addison-Wesley Publishing Company, Copyright©1995 by Sean Cotter
and Taligent,Inc. All rights
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