Computer
Hardware Question 8: What is a mainframe?
Answer: The largest, most expensive computers are known
as mainframes (see computer hardware questions 8 through 12 for information about the different types of computers).
They generally cost hundreds of thousands or even millions of dollars and they
usually are used as central data processing and storage devices by large
businesses or government agencies. The computer users can usually access the
mainframes from many different offices that can be in different buildings or
even in different cities. Many people can be in contact with the mainframe at
the same time and, at any one moment, the mainframe can be processing several
different programs for several different users. For that reason, mainframes are
often referred to as host computers in that they are host
to many users in many different locations. Many printers and a variety of
storage devices may be attached to the mainframe computer.
Businesses that process and store
large amounts of data will generally use one or more mainframe computers. For
example, banks use mainframes to keep track of checks and transactions at both
human and automated tellers (ATMs). Libraries use mainframes to keep track of
the books on hand and the ones that have been checked out. Businesses of all
sizes use mainframes to maintain inventories, accounts, and payroll.
The first computers were mainframes.
Although they were very slow - even when compared to today's low-cost personal
computers - the early mainframe computers were very large and very expensive.
Nevertheless, they were able to process data faster than anything previously
available.
Answer: Supercomputers are often grouped together with
the mainframes. But supercomputers are even more powerful (and expensive) than
most mainframes. Although they are similar in basic design to the mainframes,
they may use many processors at the same time and can process data faster than
any other type of computer. Supercomputers are generally used by very large
companies and research institutions to process complex mathematical
calculations (see computer hardware questions 8 through 12 for information about the types of computers).
Computer
Hardware Question 10: What is a minicomputer?
Answer: Minicomputers are smaller
and less expensive than mainframes. Although they may be accessed by a number
of different users just as mainframes are, there are usually fewer access sites
and the access sites are usually located in closer proximity to the
minicomputer. Because they are designed to serve the needs of many different
users, they are also referred to as host computers (see computer hardware questions 8 through 12 for information about the different types of computers).
Minicomputers are generally thought
of as medium-sized computers: while the mainframe may do the data processing
and data storage for the widespread offices of an entire large company,
minicomputers are generally limited to data processing and storage in one
location (often for one department or for a smaller company).
Like the mainframe computers,
minicomputers can serve a number of different users at the same time, but
because of their somewhat more limited capacity and speed when many users are
in contact with the minicomputer, the computer's response time may be
noticeably slower.
Mincomputers sometimes use operating
systems designed specifically for them, but many use either the UNIX or Linux
operating system (also see Computer Software Question 2: What is systems
software).
Answer: The world's newest type of computer,
the microcomputer, is now by far the most plentiful of the
three computer types (see computer hardware questions 8 through 12 for information about the different types of computers).
Known as personal computers or PCs, microcomputers come in many different sizes
and they offer users a number of different capabilities. When microcomputers
first became popular in the early 1980s, they were found mostly on individual
desks in homes and in small businesses. But soon, these "desktop"
computers began to show up in larger business and in schools and government
offices. At first, these "micros" were made by very small companies
and were sold in retail shops or through the mail. But eventually they became
so popular that just about every company that made any product that had
anything to do with electronics began to manufacture a microcomputer. Big
companies soon began to order microcomputers to attach to their mainframes and
minicomputers. This let their employees run their own programs on a
microcomputer and still maintain a data communications link with a large host
computer.
Today, micros come in all sizes and
shapes. Some have grown too large to fit on desks and now reside under the
desk. On the other hand, some of the new microcomputers are so small that you
can carry them in your pocket (but they are still referred to as
microcomputers. Sometimes more powerful microcomputers are tucked away in the
back room where they serve the function of a file server for
a group of networked microcomputers.
Regardless of their size and
appearance, all microcomputers are, basically, "personal"; that is,
they are designed to be used by one person at a time. This was the
revolutionary idea that PCs brought to the computer world. Up to that point, no
one could have conceived of the idea that individual users might have access to
their very own computer. Previously, it was part of the very concept of
computers that they were big, expensive, and that they were to be shared by
many people. Unlike mainframes and minicomputers, microcomputers generally are
not "host" to several users at the same time.
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