characteristic, interprocess communication. 5. Virtual Memory The fact that UNIX
has virtual memory allows the number of processes being executed to require more
memory than exists in the machine. 6. Graphic Interface Although not exactly a
novel characteristic of UNIX, most versions now have a graphic interface. 7.
Interplatform Support This is another characteristic that was added to UNIX
which lends the capability to execute programs from other platforms (DOS and
Windows), within the UNIX environment. 8. Networks The usual UNIX communications
protocol is TCP/IP. This allows variants of UNIX based operating systems to
communicate between themselves or with other platforms (Osiris, 1-2). CONTRAST
Both DOS and UNIX present a number of similarities, several of which shall be
addressed here. First, both systems are interactive, meaning that the shell
presents a prompt and waits for the user to enter a command. After the return or
enter key is pressed, the shell processes the command and when the command is
finished, the shell re-displays the prompt. Second, DOS batch files and UNIX
script files can be used which can store commonly used commands in a file, which
when executed, runs each command as though it has been typed from the command
line. A sequence of commands can be executed by executing the file which
contains the command(s). Third, the handling of files in both DOS and UNIX is
simplified by using wild-card characters to match files which match particular
patterns. Also, with both operating systems, users can customize and control the
behavior of the shell by using special variables that the shell supports, such
as the prompt (20,1). In addition, both systems make use of ?pipes? whose
symbol is a vertical bar ( | ). With this convention, the output from one
command becomes the input for another command. Several dissimilarities are worth
noting. As was previously mentioned, DOS is a single user, single task operating
system. Its user interface is not case sensitive, which means that commands may
be typed in either upper case, lower case or a combination of the two. UNIX
however, is a multi-user, multi-task OS. Non-interactive tasks which do not
require keyboard input can be run in the background as a separate task while the
user continues working with other interactive programs (20,1). Differing from
DOS, its user interface is case sensitive, meaning that only upper or lower case
commands must be used. APPLICATIONS & COMPUTER TYPES Whereas DOS has been
used primarily on PCs and standalone computers, UNIX can be run on single- or
multi-user computers of all sizes with a wide range of microprocessors (Flynn
& McHoes 319). UNIX is the widely supported operating system in the field of
computer science, used extensively in business as well as educational
institutions. Conversely, DOS is used mainly in businesses with older computer
systems. BENEFITS & DISADVANTAGES The major advantage that DOS has over UNIX
is its basic simplicity. Between this and the uncomplicated commands presented
by the user interface, it is a relatively simple OS to learn. DOS also has the
advantage of allowing the user to create an environment tailored strictly for
the particular task they wish to accomplish. In addition, one can customize DOS
to suit the current hardware. This can be accomplished with commands such as
date, time, prompt, path, set, assign and subst. Unlike DOS, UNIX?s main
feature is that it is a multi-user system, meaning more than one user can use
the machine at a time when supported via terminals provided by a serial or
network connection. Offering true preemptive multi-tasking, UNIX can run more
than one program at a time with a CPU that services all applications equally. In
addition, it has a hierarchical directory structure which supports the
organization and maintenance of files. Other advantages are that it has been in
the market for a number of years, and is therefore considered a stable product.
Also, due to the fact that the kernel is in ?C?, UNIX works in just about
every machine in the market, once again, making it a portable system with a
collection of very powerful utilities. Also, there are many applications
developed for DOS and UNIX which fall into the category of ?shareware?
available via the Internet (8,1). As with advantages, both DOS and UNIX have
their share of disadvantages. It can be said that DOS has two main drawbacks.
Since MS-DOS was originally written for a particular family of microprocessors,
it displays an incredible lack of flexibility and limited ability to meet the
needs of programmers and experienced users (Flynn & McHoes, 265). UNIX also
has several very distinct disadvantages. First, novice users find its commands
are almost cryptic which is interpreted as being non-?user-friendly?.
Second, the fact that there exist so many versions of the operating system means
that software producers must make several versions of their applications to
cover the greatest number of potential users. Third, UNIX is a large operating
system, and depending on the number of services installed and the functions
used, space used on a hard drive may vary from 20 Mb to 300 Mb (Osiris, 1).
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