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.