Types of Computers
Module G03c
Contents
Audience and Objectives
About this document...
When looking at this document with a Web browser,
clicking this separator will return you to the Table to Contents:
Types of Computers
There are millions of computers in existence - so many that nobody has
been able to keep track of exactly how many there are! Of those millions,
there are many difference kinds. How can we make sense of the many kinds
of computers there are? Here are some ways we can look at it:
-
What is it for?
-
Is it independent, or part of something else?
-
How "big" or "powerful" is it?
-
How "fast" is it?
What is it for?
Many computers are made to handle a wide variety of tasks, but others are
aimed at a special job or situation.
General purpose computers are designed for handling a wide variety
of tasks, such as:
-
Word processing, accounting, database
-
Payroll, inventory, order processing
-
Industrial control, engineering, drafting
-
Scientific research and data analysis
Dedicated computers are for handling one job only:
-
Word processing
-
Controlling a machine (robot)
-
Running a telephone switching station
-
Environmental control
-
Medical imaging system
Is it Independent?
When we think of "a computer," most of us probably think of machine that
is independent of other machines (though of course it could be part of
a network). But many devices that qualify as "computers" are actually a
part of something else. These are so-called embedded computers,
and most of them are actually microprocessors. So what is the difference
between a microprocessor and a microcomputer?
A computer is an independent machine containing:
-
CPU + ALU + Memory + Input + Output + Storage
They come in many sizes - tiny, small, medium, or large (see below), but
they are designed to work on their own.
An embedded processor or computer is:
-
CPU + Memory + wires to control something.
Embedded processors are found in thousands of different machines, because
they provide an inexpensive way of making the machine "smart." Here are
a few examples of the more common devices that use them:
-
Cameras
-
Microwave ovens
-
Automobile ignition, carburation, and other systems
How Big or Powerful is it?
People talk about computers in four major sizes and several subdivisions:
-
Microcomputers, most of which are also personal computers
(PCs). They are distinguished from other types by (1) a microprocessor
CPU - that is, the CPU is a single chip; and (2) they are designed
mainly to serve only one user at a time. Since these are the most
affordable and most common kind of computer, there are several types:
-
Hand-held: usually under 3 pounds or 1.5 kg. and small enough to
fit in a pocket
-
Notebook: in the 4-6 pound range (2-3 kg.) and roughly the size
of a school notebook
-
Desktop: the traditional boxy kind designed to sit on a desk (like
the College's lab computers)
-
Workstation: a more expensive, more powerful desktop microcomputer;
may be used by one person for demanding work (computer-aided engineering,
graphics animation...); or may be used as a server or minicomputer by many
people at once over a network.
-
Minicomputers are designed to do the computing for multiple simultaneous
users. Though not as large and powerful as the mainframes, they
are used by many smaller organizations for the same purpose: to do business
computing (accounting and database management). At our College, a minicomputer
is used to handle all student records and finances, including registration,
grades and transcripts, billing, and paying bills. In size, minicomputers
range from small desktop units to computers about the size of a refrigerator.
-
Mainframe computers are named for the large racks or frames that
hold their electronics. The original computers were mounted in a set of
several racks, each about the size of a large refrigerator, and the frame
containing the CPU was known as the "main frame". Computers whose electronics
occupy more than a refrigerator-sized unit are still called "mainframes",
though it is sometimes hard to distinguish a mainframe from a powerful
minicomputer.
-
Supercomputers are of course more powerful than mainframes, but
they are also built for a different purpose: research mathematics.
While mainframes are usually used for accounting and for storing large
amounts of corporate data, a supercomputer is used by university, corporate,
or government research labs, and its design function is to do the long
and tedious mathematical computations needed for that sort of work.
Keep in mind: these terms keep changing!
Today's micro has the power of...
... mini 10 years ago
... mainframe 20 years ago
How Fast is it?
Computers are valuable largely because they can do things faster. But how
do we compare one computer's speed to another's? There are two main ways
to do this - neither of them really informative, but they're the best we
have.
-
Instruction speed: (M)IPS - (Millions of) Instructions per Second.
This is often used to compare mini- and mainframe computers. (The drawback
is that on different types of computers, "instructions" do different amounts
of work.) The College's minicomputer operates at about 54 MIPS.
-
Clock speed: MHz - megahertz = millions of cycles per second. (Each
instruction 2 - 6 cycles). This is usually used with microcomputers.
Next module:
-
G04c Reading and Writing, or
-
G05c Primary and Secondary Storage
Audience:
This is for people who are curious about the different types of computers
available, and how to make sense of the wide variety. No previous background
is necessary, though fundamental terminology is helpful (as provided in
modules G01c
and G02c).
This module has been used in CIS 100
and CIS 101
Objectives
When you successfully complete this lesson, you will be able to demonstrate
understanding of...
-
The difference between general-purpose and dedicated computers
-
The difference between independent computers and embedded processors
-
The four widely-used terms for computer sizes:
-
Micro
-
Mini
-
Mainframe
-
Super
-
The fact that these terms are relative and changeable - there is no fixed
difference between these types, and historically they have changed
-
Some measures of computer capacity and how they apply to the various sizes
of computers.
About this document...
Module G03c: Types of Computers
-
Author:
-
Laurence
J. Krieg
-
Institution:
- Department
of Computer Information Systems, Washtenaw
Community College
-
Date:
-
Original: 26 Jan 1988
-
Revised with HTML: 6 May 1996
-
Minor revisions 15 Sept 1998
-
Review:
-
G03cr
-
Copyright:
-
Copyright © 1998, Laurence J. Krieg.
Instructors: You may point to this file in your Web-based materials.
Students: you may make a copy for your personal use.
All other uses: contact the author, Laurence
J. Krieg for permission.