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Computer Terms
Bit
Short for binary digit, the smallest unit of information on a machine. The term was first used in 1946 by
John Tukey, a leading statistician and adviser to five presidents. A single bit can hold only one of two
values: 0 or 1. More meaningful information is obtained by combining consecutive bits into larger units.
For example, a byte is composed of 8 consecutive bits.
Computers are sometimes classified by the number of bits they can process at one time or by the number of
bits they use to represent addresses. These two values are not always the same, which leads to confusion.
For example, classifying a computer as a 32-bit machine might mean that its data registers are 32 bits wide
or that it uses 32 bits to identify each address in memory. Whereas larger registers make a computer faster,
using more bits for addresses enables a machine to support larger programs.
Graphics are also often described by the number of bits used to represent each dot. A 1-bit image is
monochrome; an 8-bit image supports 256 colors or grayscales; and a 24- or 32-bit graphic supports true
color.
Byte
Abbreviation for binary term, a unit of storage capable of holding a single character. On almost all modern
computers, a byte is equal to 8 bits. Large amounts of memory are indicated in terms of kilobytes (1,024
bytes), megabytes (1,048,576 bytes), and gigabytes (1,073,741,824 bytes). A disk that can hold 1.44
megabytes, for example, is capable of storing approximately 1.4 million characters, or about 3,000 pages of
information.
CPU
Abbreviation of central processing unit, and pronounced as separate letters. The CPU is the brains of the
computer. Sometimes referred to simply as the processor or central processor, the CPU is where most
calculations take place. In terms of computing power, the CPU is the most important element of a computer
system.
On large machines, CPUs require one or more printed circuit boards. On personal computers and small
workstations, the CPU is housed in a single chip called a microprocessor.
Dial-Up Access
Refers to connecting a device to a network via a modem and a public telephone network. Dial-up access is
really just like a phone connection, except that the parties at the two ends are computer devices rather than
people. Because dial-up access uses normal telephone lines, the quality of the connection is not always
good and data rates are limited. In the past, the maximum data rate with dial-up access was 56 Kbps
(56,000 bits per second), but new technologies such as Cable and DSL are providing faster rates.
Dial-Up Networking
A component in Windows 95, 98 or ME that enables you to connect your computer to a network via a
modem. If your computer is not connected to a LAN and you want to connect to the Internet, you need to
configure Dial-Up Networking (DUN) to dial a Point of Presence (POP) and log into your Internet Service
Provider (ISP). Your ISP will need to provide certain information, such as the gateway address and your
computer's IP address.
Harris F. Mack
Emeritus College
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You access DUN through the My Computer icon. You can configure a different profile (called a
connectoid) for each different online service you use. Once configured, you can copy a connectoid shortcut
to your desktop so that all you need to do to make a connection is double-click the connectoid icon.
Hyperlink
An element in an electronic document that links to another place in the same document or to an entirely
different document. Typically, you click on the hyperlink to follow the link. Hyperlinks are the most
essential ingredient of all hypertext systems, including the World Wide Web.
Keyboards
The set of typewriter-like keys that enables you to enter data into a computer. Computer keyboards are
similar to electric-typewriter keyboards but contain additional keys. The keys on computer keyboards are
often classified as follows:
alphanumeric keys -- letters and numbers
punctuation keys -- comma, period, semicolon, and so on.
special keys -- function keys, control keys, arrow keys, Caps Lock key, and so on.
The standard layout of letters, numbers, and punctuation is known as a QWERTY keyboard because the first
six keys on the top row of letters spell QWERTY. The QWERTY keyboard was designed in the 1800s for
mechanical typewriters and was actually designed to slow typists down to avoid jamming the keys. Another
keyboard design, which has letters positioned for speed typing, is the Dvorak keyboard.
There is no standard computer keyboard, although many manufacturers imitate the keyboards of PCs.
There are actually three different PC keyboards: the original PC keyboard, with 84 keys; the AT keyboard,
also with 84 keys; and the enhanced keyboard, with 101 keys. The three differ somewhat in the placement
of function keys, the Control key, the Return key, and the Shift keys.
In addition to these keys, IBM keyboards contain the following keys: Page Up, Page Down, Home, End,
Insert, Pause, Num Lock, Scroll Lock, Break, Caps Lock, Print Screen.
Special Keys on PC Keyboards
Alt key
Short for Alternate, this key is like a second Control key.
Arrow keys
Most keyboards have four arrow keys that enable you to move the
cursor (or insertion point) up, down, right, or left. Used in conjunction
with the Shift or Alt keys, the arrow keys can move the cursor more
than one position at a time, but this depends on which program is
running.
Backspace key
Deletes the character just to the left of the cursor (or insertion point)
and moves the cursor to that position.
Caps Lock
Key
A toggle key that, when activated, causes all alphabetic characters to
be uppercase.
Harris F. Mack
Emeritus College
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Ctrl key
Short for Control, this key is used in conjunction with other keys to
produce control characters. The meaning of each control character
depends on which program is running.
Delete key
Sometimes labeled Del, deletes the character at the current cursor
position, or the selected object, but does not move the cursor. For
graphics-based applications, the Delete key deletes the character to the
right of the insertion point.
Enter key
Used to enter commands or to move the cursor to the beginning of the
next line. Sometimes labeled Return instead of Enter.
Esc key
Short for Escape, this key is used to send special codes to devices and
to exit (or escape) from programs and tasks.
Fn key
Short for Function, this key is used in conjunction with other keys to
produce special actions that vary depending on which program is
running. This key is found most frequently on portable computers that
do not have full-size keyboards.
Special keys labeled F1 to Fx, x being the number of function keys on
Function Keys the keyboard. These keys have different meanings depending on which
program is running.
Return key
Another name for the Enter key.
Memory
Internal storage areas in the computer. The term memory identifies data storage that comes in the form of
chips, and the word storage is used for memory that exists on tapes or disks. Moreover, the term memory is
usually used as a shorthand for physical memory, which refers to the actual chips capable of holding data.
Some computers also use virtual memory, which expands physical memory onto a hard disk.
Every computer comes with a certain amount of physical memory, usually referred to as main memory or
RAM. You can think of main memory as an array of boxes, each of which can hold a single byte of
information. A computer that has 1 megabyte of memory, therefore, can hold about 1 million bytes (or
characters) of information.
There are several different types of memory:
RAM (random-access memory): This is the same as main memory. When used by itself, the
term RAM refers to read and write memory; that is, you can both write data into RAM and read
data from RAM. This is in contrast to ROM, which permits you only to read data. Most RAM is
volatile, which means that it requires a steady flow of electricity to maintain its contents. As soon
as the power is turned off, whatever data was in RAM is lost.
ROM (read-only memory): Computers almost always contain a small amount of read-only
memory that holds instructions for starting up the computer. Unlike RAM, ROM cannot be written
to.
PROM (programmable read-only memory): A PROM is a memory chip on which you can
store a program. But once the PROM has been used, you cannot wipe it clean and use it to store
something else. Like ROMs, PROMs are non-volatile.
EPROM (erasable programmable read-only memory): An EPROM is a special type of
PROM that can be erased by exposing it to ultraviolet light.
Harris F. Mack
Emeritus College
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Mouse
A device that controls the movement of the cursor or pointer on a display screen. A mouse is a small object
you can roll along a hard, flat surface. Its name is derived from its shape, which looks a bit like a mouse, its
connecting wire that one can imagine to be the mouse's tail, and the fact that one must make it scurry along
a surface. As you move the mouse, the pointer on the display screen moves in the same direction. Mice
contain at least one button and sometimes as many as three, which have different functions depending on
what program is running. Some newer mice also include a scroll wheel for scrolling through long
documents.
Invented by Douglas Engelbart of Stanford Research Center in 1963, and pioneered by Xerox in the 1970s,
the mouse is one of the great breakthroughs in computer ergonomics because it frees the user to a large
extent from using the keyboard. In particular, the mouse is important for graphical user interfaces because
you can simply point to options and objects and click a mouse button. Such applications are often called
point-and-click programs. The mouse is also useful for graphics programs that allow you to draw pictures
by using the mouse like a pen, pencil, or paintbrush.
There are three basic types of mice:
1.
2.
3.
mechanical: Has a rubber or metal ball on its underside that can roll in all directions. Mechanical
sensors within the mouse detect the direction the ball is rolling and move the screen pointer
accordingly.
optomechanical: Same as a mechanical mouse, but uses optical sensors to detect motion of the
ball.
optical: Uses a laser to detect the mouse's movement. Optical mice have no mechanical moving
parts. They respond more quickly and precisely than mechanical and optomechanical mice, but
they are also more expensive.
Mice connect to PCs in one of three ways:
1.
2.
3.
Serial mice connect directly to an RS-232C serial port or a PS/2 port. This is the simplest type of
connection.
PS/2 mice connect to a PS/2 port.
USB mice connect to a USB port.
Cordless mice aren't physically connected at all. Instead they rely on infrared or radio waves to
communicate with the computer. Cordless mice are more expensive than both serial and bus mice, but they
do eliminate the cord, which can sometimes get in the way.
Clicking on a mouse
To tap on a mouse button, pressing it down and then immediately releasing it. Note that
clicking a mouse button is different from pressing (or dragging) a mouse button, which
implies that you hold the button down without releasing it. The phrase to click on means
to select (a screen object) by moving the mouse pointer to the object's position and
clicking a mouse button.
Some operations require a double click, meaning that you must click a mouse button
twice in rapid succession. Shift clicking refers to clicking the mouse button while holding
the Shift key down.
Harris F. Mack
Emeritus College
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Operating System
The most important program that runs on a computer. Every general-purpose computer must have an
operating system to run other programs. Operating systems perform basic tasks, such as recognizing input
from the keyboard, sending output to the display screen, keeping track of files and directories on the disk,
and controlling peripheral devices such as disk drives and printers.
For large systems, the operating system has even greater responsibilities and powers. It is like a traffic cop,
making sure that different programs and users running at the same time do not interfere with each other.
The operating system is also responsible for security, ensuring that unauthorized users do not access the
system.
Operating systems provide a software platform on top of which other programs, called application
programs, can run. For PCs, the two most popular operating systems are Microsoft Windows (95,98, ME,
SE, XP) and Apple Computers (Macintosh).
Microprocessor
A silicon chip that contains a CPU. In the world of personal computers, the terms microprocessor and CPU
are used interchangeably. At the heart of all personal computers and most workstations sits a
microprocessor. Microprocessors also control the logic of almost all digital devices, from clock radios to
fuel-injection systems for automobiles.
Three basic characteristics differentiate microprocessors:
Instruction set: The set of instructions that the microprocessor can execute.
bandwidth : The number of bits processed in a single instruction.
clock speed : Given in megahertz (MHz), the clock speed determines how many instructions
per second the processor can execute.
The higher the values, the more powerful the CPU.
Personal Computer (PC)
Personal computers first appeared in the late 1970s. One of the first and most popular personal computers
was the Apple II, introduced in 1977 by Apple Computer. During the late 1970s and early 1980s, new
models and competing operating systems seemed to appear daily. Then, in 1981, IBM entered the fray with
its first personal computer, known as the IBM PC. The IBM PC quickly became the personal computer of
choice, and most other personal computer manufacturers fell by the wayside. One of the few companies to
survive IBM's onslaught was Apple Computer, which remains a major player in the personal computer
marketplace.
Web Page
A document on the World Wide Web. Every Web page is identified by a unique URL (Uniform Resource
Locator).
Harris F. Mack
Emeritus College
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Web Site
A site (location) on the World Wide Web. Each Web site contains a home page, which is the first document
users see when they enter the site. The site might also contain additional documents and files. Each site is
owned and managed by an individual, company or organization.
World Wide Web (WWW)
A system of Internet servers that support specially formatted documents. The documents are formatted in a
language called HTML (HyperText Markup Language) that supports links to other documents, as well as
graphics, audio, and video files. This means you can jump from one document to another simply by
clicking on hot spots. Not all Internet servers are part of the World Wide Web.
There are several applications called Web browsers that make it easy to access the World Wide Web; Two
of the most popular being Netscape Navigator and Microsoft's Internet Explorer.
Harris F. Mack
Emeritus College
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