Networking: A Beginner's Guide
Most database programs do allow multiple users to access a database simultaneously.
Often, this is done using a technique called row locking, which restricts changes to any given record
to only one user at a time.
Network operating systems that perform file sharing also administer the security
for the shared files. This security can control, with a fine level of detail, who has access
to which files and what kinds of access they have. For example, some users might have
permission to view only certain shared files, while others have permission to edit or
even delete certain shared files.
A close runner-up in importance to file sharing is printer sharing. While it is true that
laser printers are currently so inexpensive that you can afford to put one in every
office if you wish, sharing laser printers among the users on the network is still more
Printer sharing enables you to reduce the number of printers you need and also to
offer much higher-quality printers. Newer digital copiers that can handle large print
jobs at more than 80 pages per minute and provide special printing features can cost
more than $20,000. Sharing such printers among many users makes sense.
Printer sharing can be done in several ways. The most common way is to use print
queues on a server. A printer queue holds print jobs until any currently running print
jobs are finished, and then automatically sends the waiting jobs to the printer. Using
a print queue is efficient for the workstations because they can quickly print to
the print queue and don't need to wait for the printer itself to process any waiting
Another way to share printers on a network is to let each workstation access the
printer directly (most printers can be configured so they are connected to the network
just like a network workstation). In this case, usually each workstation must wait its
turn if many workstations are vying for the printer.
Networked printers that use printer queues have a print server that handles the job
of sending each print job to the printer in turn. The print server function can be filled in
a number of ways:
By a file server that is connected either directly or across the network to the
By a computer connected to the network, with the printer connected to that
computer. The computer runs special print server software to perform this job.
Through the use of a built-in print server on a printer's network interface
card (NIC), which contains the hardware necessary to act as a print server. For
example, many laser printers offer an option to include a NIC in the printer.
This is far less expensive than dedicating a stand-alone computer to the job.