nation, the costs are distributed over many users, reducing overall costs. Some
timesharing systems are designed for, owned by, and used exclusively within a single
organization, such as a university which provides access to the staff and students.
Other systems are remote, that is, accessed through long distance phone connection.
time-sharing: an arrangement in which two or more users can access the same
central computer resources and programs, and receive what seems to be
b. Advantages and Disadvantages. Time-sharing reduces CPU idle time,
while offering computer capability to small users. Each user (station) pays for real time
on-line access to a central processor, and a library of applications programs. A
disadvantage of time-sharing is that it becomes very expensive as data-processing
needs increase. The more computer time required, the greater the monthly costs.
c. How It Works. In time-sharing, a number of independent, relatively low-
speed stations have access to a CPU and its programs. Multiple users can be
accessing the same programs simultaneously. But other users cannot access your data
storage. Basically, time-sharing works by dividing up a period of time, such as a
second, among many users. Each user gets a fraction of every second devoted to him
or her exclusively. Since input/output operations from peripheral devices and terminals
are very slow compared to the electronic speed of the computer, the fraction of a
second is sufficient to handle the user's primary storage and processing requirements.
None of the many users is even aware that other users are getting time. This gives the
user the impression that he or she has the entire machine to himself or herself.
d. Bulletin Board System. A bulletin board system (BBS) is a form of remote
time-sharing that links computers though dedicated phone lines. The computer
answers the phone, verifies the user's identity, checks what he or she did the last time,
keeps track of the length of the interaction, and ensures that the user logged out
appropriately. The computer can handle multiple users at the same time who may be
playing games, researching term papers, etc.
remote system: a communication system in which the terminals are widely
separated so that telephone lines, microwave stations, or satellites must be used
to link up to the central computer.
a. A mainframe may be linked to its peripherals (input/output devices, auxiliary
storage devices, and so forth) either directly by coaxial or other cables or through
communication channels. In local or Local Area Network (LAN) systems, peripherals
are connected directly to the CPU(s). They are within the same building and linked by
cables. In remote systems, far removed terminals are linked to the central computer by
communication channels. The CPUs) is (are) not in the same building.