Information Technology Reference
In-Depth Information
So how do different operating systems influence access to files?
As we consider this question, let's review the previous points more
closely. This chapter has examined the use of computers attached to
a network to communicate. Such communication involves several
logical layers—often involving the standards called TCP and IP that
we will discuss shortly. Although these standards provide many ca
pabilities, they require that machines be physically connected to net
works, and those networks in turn must be connected to each other
for communication to take place.
Sometimes within a lab or an office, computers may be con
nected to each other, but not to the outside world (the Internet). For
example, computers in a law office or medical facility may not be
connected to the Internet as a mechanism to prevent unauthorized
access to sensitive information. As another example, computers for
a college course on networking may be connected to each other, but
not to machines outside the lab. This configuration would allow
students to learn about details of networks and to run experiments
without interfering with computers and users outside the lab when
something goes wrong.
Even when machines can communicate with each other, operat
ing systems maintain records of who is allowed to access what data,
as noted in Chapter 3. Typically, the person who creates a file has
complete authority to view and change the data; however, others
also may be allowed to read or to modify the information. When
such permission is granted, others might use FTP or remote file ac
cess to view or edit the material. Note, however, that permission to
view or modify one file does not necessarily carry over to the same
permission for another file. Thus, it is quite possible that you could
read or even change one file on a remote machine but not have the
same privileges for another file.
Further, the ability to view a file's contents does not immedi
ately imply that the file is intelligible. For security reasons, some in
formation may be stored in an encrypted form, so the material
makes sense only if you or your software knows how to decode the
stored material. (More about this in the next chapter.)
In addition, various programs may place data in one format or
another to enhance processing. For example, word processors often
insert information on fonts and spacing within files. The format, for
that information, however, may vary remarkably from one word
