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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 standard. 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.

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