Monday, December 5, 2011

Computer Glossary

This long promised glossary is not alphabetical since that doesn't work very well for this type of material. It is loosely organized in some logical groupings but it is short enough that the best approach is just to skim the words in the left column to find ones you've heard and wondered about. Often it seems like you are the only one in the room that doesn't know what the "cloud" is but you are not alone. Here's your chance to catch up and get ahead of most of the people you encounter.

Mobile Devices
Smartphones and Tablets are the most talked about mobile devices today. In a word, they are computers that are portable in the extreme. They have processors, memory, operating systems, keyboards and touchscreens for data entry and for displaying the output. Most importantly, to qualify as general-purpose computers they allow user installation of programs (apps in today’s vernacular). Without this last requirement some current refrigerators – and future toasters – would likely qualify as general-purpose computers.
Tablets are at the large end in terms of mobile screen size – typically seven to ten inch diagonal measurement. The other primary difference from smartphones is that tablets generally don’t have a connection to a cell phone network and if they do it’s not used for phone calls – just for Internet activities. There is nothing stopping a company from putting a cell phone capability into a tablet. Two reasons they probably won’t: the tablet war is turning into a price war and every penny they can cut from the cost is a penny they can keep; the idea of talking into a tablet just seems strange and most tablet owners have or will have a cell phone. Nomenclature will be confusing for a while since someone could – and probably will – put telephone circuitry into a ten inch tablet or remove it from a four inch smartphone.
Phone - Smartphone
Smartphones allow users to install apps of their choosing
Phone – Feature phone
Feature phones can perform tasks using the Internet such as email and web surfing. They come with a fixed set of apps – calendar, contact list, etc.
Phone – Cell phone
Simple cell phones are used only for making phone calls.
Cell phone contracts
Many phones receive service from one of the carriers (AT&T, Verizon, etc.) based on a contract. Monthly charges are based on four elements.
1)    Number of minutes of call time
2)    Number of text messages
3)    Amount of information sent and received (the dataplan)
4)    Fees and taxes
Dataplans are likely to cause significant confusion in the future since we are using mobile devices more frequently and very few people know how many megabytes are in a video.
Traditional cell phones do not require dataplans. Prepaid cellphones are traditional cell phones that allow you to buy minutes in advance. These are individuals with limited need for a cell phone.
Internet TV
Much of our television in the future will come through the Internet. A simple computer can be incorporated into a TV set or offered as a standalone box. No matter the form, these are real computers – generally with limited storage. Content is streamed from the Internet not stored locally. They use the TV as a display and a remote control or keyboard for input. Some have relatively simple choices while others offer a full web browser on the TV.
An app is just a new name for a program. You used to install programs; now you install apps.
Operating System - OS
All computers including desktops, laptops, smartphones and tablets have a program called the operating system (OS). In the past the three best-known computer operating systems were Windows, Mac and Linux. Currently the top mobile operating systems are Google’s Android and Apple’s iOS. There are at least ten mobile operating systems today but few are likely to survive very long.
UI – User Interface
Ever since Apple introduced the graphical user interface in 1984 (icons manipulated with a mouse on a “desktop”) the User Interface (UI) has been critical. Methods of interacting with a computer (using a mouse and keyboard) have progressed slowly in recent years but touchscreen technology is changing the UI at lightening speed.
Wireless connections WiFi, Bluetooth, etc.
All of these are just the various types of radio signals that are used to connect devices wirelessly. They’re called radio signals since they were used for radios decades before computers were invented. For a more detailed explanation check out my July blog post.
In the simplest terms the Cloud means storing information and running problems on the Internet rather than your PC. For the professionals it is much more complicated and you can read more in my June 2011 Newsletter.
Internet and the World Wide Web (Web)
The Internet consists of millions of computers connected together. They may be gigantic machines but even your personal computer is an Internet computer when it is online.
The World Wide Web consists of software and files that allow anyone to use Internet computers to store and retrieve information - information that might be text, photos, music, etc.
A web server is one of the most important web programs since it sends files (web pages) to you when you click on a link or type an address into your browser. It sends (or serves) the page to you and then waits patiently in case you want another file – possibly serving thousands of files to other users in the meantime.
Sending and retrieving web files is only one use of the Internet. Email is another. Email uses the Internet but not necessarily the web. This situation is somewhat confusing since many email services are now available through your web browser.
If two computers (or two people) are going to work well together, they have to agree on how they will do things. Often these agreements are called protocols.  Who sits where at a state dinner is determined by the protocol for state dinners. In the case of computers, how they exchange information is called a protocol that is described first on paper – which signals are going on which wires, etc. To be able to communicate both computers must have a program that implements a particular protocol. Basically it’s a description of what characters will travel between the two computers and in what order. You may hear about IP addresses – these are the addresses used by all computers on the Internet (even yours) according to the Internet Protocol.
We all remember making up secret codes at a very young age. Encryption is just the name for a myriad of techniques that can transform a message – text, photo, etc. – so it cannot be understood if it falls into the wrong hands. Breaking enemy codes was a major undertaking in World War II and today any spy agency worth its salt is doing the same thing with information intercepted on the Internet.
Units – Bit, Byte and Megabyte
We’ve heard that all information in a computer is stored as zeros and ones. If you put enough zeros and ones together you can represent a text book or reproduction of the Mona Lisa. If you take an image from your digital camera or off the Internet and enlarge it many, many times, you will see individual picture elements, (pixels or dots). Each pixel is a single color and that color is represented by a number – a string of zeros and ones.
Storage space for a single zero or one is called a bit – just like storage space for a number from 0-9 is referred to as a digit.
A group of eight zeros and ones is referred to as a byte. As a rough approximation a single character of text can be represented by a combination of zeros and ones stored in one byte (a=00000001, b=00000010, etc.)
A kilobyte is roughly one thousand bytes; a megabyte is roughly one million bytes and a gigabyte is roughly one billion bytes. I say roughly because there are two definitions for each of those terms but they are similar enough for most people to ignore.
A pixel is a single point (dot) in an image. A ten megapixel camera can take pictures with approximately ten million pixels. Each pixel requires several bytes of memory to record the color – see pixel depth.
Pixel depth
Each pixel (dot in an image) can represent millions of different colors. The value stored for each pixel indicates the color of that dot. The higher the pixel depth (more bits to store the value), the more colors that a pixel can represent. For example, if you stored the color of a pixel as a two digit number, you could store up to 100 different colors – 00-99. Computers store values in binary but the principal is the same.
Compression (JPEG or JPG for still pictures and MPEG for videos) In practice there are many other compression standards.
Storing a color value for every pixel in an image results in very large files. It is common practice to compress the image by, for example, indicating that a large area of sky is blue with only a few values – the numeric value for blue color and the boundaries of the block of sky. A tiny speck of a bird in the sky might just be tossed out in the process. The higher the compression, the smaller the resulting file and the more image points will be lost or modified.
Videos can have each individual frame compressed in this way but add interframe compression; if two successive frames are nearly identical, only the changed pixels are included for the second frame.
Generally used to describe high speed Internet access with a variety of speeds. Usually contrasted with dialup connections.
The telephone system was originally intended to transmit human voices. When we began sending information between computers over phone lines, there had to be a way of changing zeros and ones to sound patterns (called modulating) when they were sent and then back into zeros and ones (demodulating) at the other end. The device we use is a modulator/demodulator (modem) - one at each end of the line.
If there are multiple computers in your home or office and only one Internet connection, you need a way to keep transmissions separated. Signals from a computer connected a wireless network go first to the router which attaches a numeric code to indicate which computer sent it. When a response to that transmission is received over the Internet it comes back through the modem and then to the router to send it to the correct computer. Today modems and routers are usually combined into a single device that does both jobs.
A file type indicates what type of program created or can read a particular file - .doc for MS Word, .xls for Excel, etc. Files that come over the Internet to be displayed by a browser like Internet Explorer, Firefox or Safari use .html or .htm as a file type.
Flash is a type of file often used for video but for other purposes as well. Flash is losing favor as other more modern programming tools are developed, e.g. HTML v5.
PDF files
The pdf file type was developed in response to the many incompatible file types that were causing confusion. The idea was that all computers could have a pdf file “reader” so any document – word processing, spreadsheet, etc. – that could be converted to a pdf format could be read on any computer.
A Uniform Resource Locator is the fancy name for the Internet addressing scheme. You could type an address into your web browser and call it either an address or URL. URL is the cooler term.
Smartphones and tablet computers use display screens that can detect the touch of a finger or special soft stylus. They can be programmed to respond to various gestures – tap and double tap, as well as sliding motions involving several fingers. Cheaper touchscreens require pressure but later, higher quality screens respond to a very light touch. Touch gestures often imitate mouse clicks – double click/double tap, click and drag/tap and drag, etc.
Domain Names
To provide some structure to Internet addressing, the scheme starts with Top Level Domains. These include .com, .edu, .mil, .gov and .biz - called generic TLDs. They are not associated with any country. TLDs also include two letter country codes .us, . ca. ru, etc. New top level domains are just being rolled out now.
Any organization that wants an Internet address can apply for its own name – or – consisting of a specific name associated with one of the TLDs. Needless to say most common words and proper names are already taken.
This is how requests for information are routed around the Internet. is essentially a folder of files stored somewhere on the Internet. One of those files is the home page that will be retrieved if no further information is provided. In most cases, someone might want a specific file and request This is a file in the folder
www, http, https, ftp
A web file usually starts with www (world wide web) but if you leave that out, your browser will generally insert it for you. The Internet operates on Hypertext Transport Protocol - http -but again the browser will often add that to an address. Secure web sites use https and it is important to put that in to access those sites. FTP is the file transfer protocol – not a web service – which at one time required a separate – non-browser – program. But like many other services, FTP can usually be handled by your web browser.
A web browser was once a program with one purpose – to display files ending in htm or html. These programs have been greatly expanded to perform numerous other functions – see FTP above.
Email and web capitalization
Email addresses are NOT case sensitive. Web addresses are NOT case sensitive up to the first slash following the .com, .gov, .us, etc. Following that slash they may or may not be case sensitive so you need to assume they are unless you know otherwise. is never case sensitive but the “file1.htm” in is likely case sensitive.


  1. Gary,
    As always, you make every question OK to ask. Thanks for making things clear and simple in this increasingly blurry and complex technical world!

  2. Andrea - I'm really sorry for the long delay in responding to your note. Thanks very much for your kind words. Please let me know if there's anything you'd like more information about. Take care and happy holidays.