Interframe
compression
Technique for compressing video files that eliminates redundant data between
successive frames.
Intraframe
compression
Technique for compressing video that eliminates redundant data within a frame.
JPEG A lossy-compressed bitmapped image file format developed by the Joint
Photographic Experts Group. Supports 24-bit color.
KaZaA A peer-to-peer file-sharing application.
Limewire A peer-to-peer file sharing application.
lossless
compression
A method of compressing file information without losing any data.
lossy
compression
A method of compressing file information that results in some data loss.
MIDI Musical Instrument Digital Interface. An audio file format.
MP3 MPEG, Audio Layer 3. A compressed audio file format that offers a
compression ratio of about 1:12.
MPEG A compressed video file format developed by the Moving Picture Experts
Group. Several variants exist, including MPEG-1 (commonly used for
downloadable movie clips), MPEG-2 (the file format used by DVDs), and
MPEG-4 (increasingly used for downloadable movies).
multimedia The combination of more than one presentation format (e.g., text, images, sound,
and video).
Napster Originally a file-sharing application, it is now a music subscription serivice.
PICT An image file format for the Mac platform.
PNG Portable Network Graphic. A losslessly compressed bitmapped image file
format meant to be a patent-free successor to GIF.
QuickTime A video file format developed by Apple.
RealAudio A streamable audio file format developed by Real Networks.
RealVideo A streamable video file format developed by Real Networks.
streaming Mechanism for playing video or audio files over a network that allows packets to
be played as they are downloaded, eliminating the need to download the entire
file before playing.
TIFF Tagged Image File Format. A lossless image file format commonly used for
faxes and high-resolution graphics.
vector graphic An image file format based on the mathematical expression of geometric
elements (lines, arcs, polygons)
WAV An audio file format commonly used for Windows sounds.
WMA Windows Media Audio. A compressed audio file format developed by
Microsoft.
WMV Windows Media Video. A compressed video file format developed by Microsoft.
Security
adware Software (typically installed without a user’s knowledge or consent) that displays
advertisements (such as browser popups).
cookie A small file given to a web browser by a webserver used to store information like a
user ID or preferences for customized web pages.
cracking Breaking into or circumventing a computer system (such as copy protection).
form Just like a company would use a paper form to collect information voluntarily, a
webpage uses a form for a user to enter information to submit to the company over
the Internet.
hacking Forcefully entering into a computer system to access (or modify) its data without
consent. Originally, this term actually had a positive connotation for programmers
with the ability to modify an existing program to achieve a new goal.
log A file that keeps track of application or system events, often used to track usage or
troubleshoot problems.
malware A general category of malicious software that can attack your computer in various
ways. Virus, spyware, and worms are all considered malware.
packet
sniffing
The act of intercepting others’ network packets and reading them, allowing a person
to read another’s email, view the same websites, read conversations, among other
things.
phishing Obtaining an innocent user’s account information by falsely acting as a legitimate
company or website. (Consider fishing in a sea of users by giving bait as a legitimatelooking
email to obtain information.)
piracy Illegally reproducing copyrighted work. Music, photographs, movies, and software are
all potentially copyrighted and can be pirated.
privacy A reasonable expectation that sensitive or personal information is kept safe and only
pre-determined people are allowed to access, view, or edit it.
processor serial
number
A unique identifier imprinted in the hardware of a processor, potentially
accessible by software.
registration
code
A unique code provided to every legitimately purchased copy of software. It can
be used to ensure legality and prevent piracy.
security Protecting a computer so that only authorized users are allowed to view and edit
its information.
serial number A unique identifier that, if registered with the manufacturer, can identify the
purchaser, often used by hardware and software manufacturers for warranty
eligibility.
spyware Malware that stealthily obtains information on a user’s identity or activities
without consent, often submitting thereafter to a database. Originally intended
to be harmless, to help target users for advertising.
virus Malware with the ability to self-replicate, but it generally cannot self-propagate to
other computers. Usually a user must assist it by sharing infected files or media.
warez An application that normally has tight copy protection to prevent piracy
becomes warez when it is cracked and made freely (and illegally) available online.
worm Malware with the ability to self-replicate and self-propagate through a network
and attack other computers (e.g., by sending a copy of itself to everyone in a
user’s address book).
zombie An infected computer that floods another computer with packets in an attempt
to infect or crash it without the consent or knowledge of the infected computer’s
owner.
Website Development
AJAX Asynchronous JavaScript and XML. A framework that enables web pages to exchange
data with a web server without reloading the entire page, thereby creating a more
seamless experience for a visitor.
Apache Apache Software Foundation, a non-profit corporation that oversees several important
software projects, one of which is the Apache HTTP Server, the world’s most popular
web server.
ASP Active Server Pages. Microsoft’s server-side scripting technology for dynamically
generated web pages. An add-on to IIS.
attribute An optional modifier of an HTML or XHTML element. Each attribute necessitates a
value, and an element may have zero or more attributes.
C++ A programming language developed in the 1980s by Bjarne Stroustrup of Bell Labs. It
originates from two older programming languages, C and Smalltalk, combining the
computing power and low-level functions of the former with the object-oriented model
of the latter. C++ used to be the most popular programming language for about a
decade, losing some of its advocates to Java and C#.
CGI Common Gateway Interface. A standard for passing data between a client and a
webserver. Allows a client’s web browser to use data from a program executed on the
web server.
CSS Cascading Style Sheets. A language used to describe the presentation of a document
written in a markup language. Commonly used to style webpages written in HTML or
XHTML.
DHTML Dynamic HTML. Denotes a collection of technologies collectively used to create
dynamic web pages. These technologies include a static markup language (HTML or
XHTML), a stylesheet language (CSS), and a client-side scripting language (JavaScript).
doctype Document Type Declaration. A declaration that associates a markup document with its
type definition. A doctype declaration has to present in all XHTML documents for
them to be valid.
element A lexical unit of an HTML or XHTML document demarcating its content.
Elements generally consist of three parts: a start tag marking the beginning of an
element, some amount of content, and an end tag.
hexadecimal
Of or relating to the base-16 numeric system. Uses the digits 0 – 9 and the letters
a – f (to represent the values 10 – 15). For example, the hexadecimal number 3f is
63 in decimal (3x16 + 15) and 00111111 in binary.
HTML HyperText Markup Language. A markup language used to create webpages
viewable in a browser. Structures information with tags, denoting parts of text as
headings, paragraphs, hyperlinks, etc.
httpd Apache’s HTTP server.
IIS Internet Information Services. A set of Internet-based services for Microsoft
Windows-based servers, and the second most popular webserver after Apache.
Java A programming language developed by James Gosling and his team at Sun
Microsystems. Its stricter object model, easier syntax, and powerful networking
features made the language a strong competitor to C++. Java is, arguably, the most
popular computer language today.
JavaScript An object-oriented programming language mostly used to create dynamic content
in web pages. It has C-like syntax and is similar to other scripting languages, having
little to do with Java, despite its name.
JSP JavaServer Pages. A Java-based technology that allows for dynamic generation of
HTML and XHTML.
octal Of or relating to the base-8 numeric system. Uses the digits 0 – 7. For example,
the octal number 125 is 85 in decimal (1 82 + 2 81 + 5 80) and 55 in
hexadecimal.
parse To analyze a stream of input (such as a computer program) to determine its
grammatical structure and break it down into individual tokens.
Perl Procedural programming language created by Larry Wall. Its compact syntax and
large collection of text-processing functions make it the language of choice for
quick information-processing scripts, but it may not be feasible to creating largescale
applications. It has been “backronymed” as Practical Extraction and Report
Language.
PHP “PHP: Hypertext Processor” (a recursive acronym) or “Pretty Hypertext
Processor”. A programming language used to create server-side applications and
dynamic web content. A popular alternative to Microsoft’s ASP technology.
pretty-print To present an object (such as a webpage, or part thereof) in such a manner as to
make its structure easier to perceive (e.g., nicely indented with frequent line breaks).
property A feature of an HTML or XHTML element that can be controlled by CSS;
a property has a value associated with it, usually written as property: value.
script A program written in a scripting programming language.
SSI Server Side Includes. A server-side scripting language primarily used to include
contents of a file.
stylesheet A language used to describe the style of elements in a document marked up using a
markup language. CSS is the widely used stylesheet language for HTML and
XHTML today.
tag A label used to include metadata to the contents of a document. In HTML and
XHTML, tags are used to demarcate the beginning and end of a certain
representation of information. For example all text between the <b> and </b> tags
will be bold, and everything between the <p> and </p> tags will be considered a
paragraph. Many tags also have a set of optional attribute="value" pairs.
valid An XHMTL document is said to be “valid” if it conforms to a doctype
(i.e., contains no errors).
web-safe
colors
Any of the 216 colors originally used in webpages.
webserver A computer that receives HTTP requests from clients’ web browsers, and in return
serves them webpages, which are usually HTML or XHTML documents. Also, a
computer program that provides the functionality just described.
well-formed An XHTML document is said to be “well-formed” if, among other things, all
elements’ and attributes’ names are in lowercase, all attributes’ values are flanked by
single or double quotes, and all tags are balanced.
XHTML eXtensible HyperText Markup Language. Has the same expressive capabilities as
HTML, but a stricter syntax, which allows for better automation of data processing.
Specifically, XHTML requires that all webpages written in it be well-formed.
Programming
algorithm A procedure used to solve a problem or perform a task. For example, Google’s
web search tool has an algorithm for searching webpages and ranking them by
relevance.
application A program meant for use by a person (e.g., a word-processing application as
opposed to system software).
argument A parameter used to specify with greater precision how a function or method
should behave.
branch A point in a program where the next line of instruction might not be the next
sequential line because of a condition that must be evaluated (e.g., if a is true then
do b, else do c).
bytecodes Machine-independent, compiled code that is intended to be used by an
intermediate rather than a CPU. For example, Java bytecodes are executable by the
Java Virtual Machine.
C A high-level programming language developed in the early 1970s by Ken
Thompson and Dennis Ritchie for use on the UNIX operating system. It has
become an industry standard used on many platforms.
C# An object-oriented programming language developed by Microsoft and based on C
and C++.
C++ An object-oriented programming language based on C.
code A set of computer instructions written in a programming language.
compiler A program that takes humanly readable code and converts it into machine code.
condition A requirement or qualification, the value of which determines the branch of
instructions to follow (e.g., if a is true then do b, else do c).
decrement To decrease the value of a variable (usually by 1).
event An action (e.g., “mouse down” in Scratchspeak) that must occur in order for some
other action to happen.
function A sequence of instructions that are part of a larger program. Functions can “call”
(i.e., execute) other functions. Typically, a function is dedicated to a particular task.
increment To increase the value of a variable (usually by 1).
instruction A statement that tells a computer what to do (e.g., ADD).
interpreter A program used to run other programs by ingesting uncompiled code in real-time
rather than using compiled code.
Java A platform-independent, object-oriented programming language developed by Sun
Microsystems.
JavaScript An interpreted language created by Netscape to add functionality and dynamism to
web pages. JavaScript is not related to Java. At all. Not one bit. Please don’t call
JavaScript “Java”!
language A set of “vocabulary” and rules with which a computer can be instructed to
perform tasks.
library A collection of “helper” programs called by an executable.
loop A cycle of instructions in a program.
method A named piece of code that is associated with a class or an object in objectoriented
programming.
object A conceptual entity in object-oriented programming that has associated with it data
and/or actions.
object code Machine-readable instructions generated by a compiler.
parameter A mechanism with which the behavior of a function or method can be modified.
Perl Practical Extraction and Reporting Language. A language commonly used in
scripts and CGI applications.
program A set of instructions that compels a computer (perhaps at a user’s bidding) to
perform some task(s).
programmer One who writes programs.
programming The act of writing a program.
pseudocode A short-hand way of writing a program without the precise syntax of a formal
programming language. Writing “plain English” pseudocode is a good way for
new programmers to understand the logic behind their programs.
Scratch A “programming language that lets you create your own animations, games, and
interactive art” developed by the Lifelong Kindergarten Group at the MIT Media
Lab.
script A program written in an interpreted language. The term sometimes implies a short
program.
software See program.
source code The textual form of a program as written by its programmer(s).
statement An instruction in a program that compels the program to do something (e.g.,
Scratch’s “say ... ” block).
thread Part of a program that can execute simultaneously with other parts.
variable A symbolic representation of or placeholder for an unknown value in a program.