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Unformatted text preview: ace that facilitates the transmission of data over telephone lines. Many serial ports installed on PC systems follow this
2. Parallel ports. Parallel ports facilitate the parallel transmission of data, that
is, 8 or more bits are transmitted simultaneously. A popular parallel port standard
is the Centronics printer interface. Parallel ports provide the interface for such
devices as high-speed printers and plotters, magnetic tape backup units, and
external hard disk units.
The popular operating systems for PCs are MS-DOS, MS-Windows, WindowsNT, Linux and Unix. An OS called OS/2 was also used on IBM PCs few years ago
and the Apple's Macintosh PCs run the Apple's propriety OS called Macintosh OS
as well as Apple's version of Unix called A/UX. Most of these operating systems
enable the user to switch between tasks. This capability is known as multitasking a single-user variation of the multiprogramming concept. Multitasking eases user
operation and saves lots of time when a user has to switch between two or more
applications while performing a job. For example, suppose a user is using a word
processor to create an annual report, and he/she needs to do some arithmetic
calculations on the computer and include the calculated results in the report.
Without multitasking, the user would have to close the annual report file and the
word processing application, open the calculator application, make the necessary
calculations, write down the results, close the calculator application, and reopen
the word processing application and the annual report file. With multitasking, the
user simply opens the calculator application, makes the necessary calculations, and
switches back to the annual report file to continue working on it. This capability to
switch between tasks (applications) saves lots of time and effort of the user. If
hard disk space is sufficient, a PC can be configured to simultaneously have more
than one OS. For example, a PC can be configured to have both MS-Windows and
Linux OS and the user can choose at the time...
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This document was uploaded on 04/07/2014.
- Spring '14