Computers 101

A simplified explaination about personal computers

By Matthew Stanton, Metromemetics LLC
(first posted 01/14/2001; revised 01/20/2003)

Interactive designers have to understand the number one component of today's electronic media: the personal computer.

Just for the purposes of the following explanation, here's a limited definition: A personal computer is a device with a keyboard, monitor screen, and internal drive which allows users to run software and save their electronic documents for use again later. The hardware capabilities of a computer are measured by three things: its processor speed, the amount of RAM memory installed, and the amount of hard drive memory available for storing program files. These three "physical" factors depend on the type of plastic and silicon actually sitting inside the computer's main box:

processor speed: The chip which determines how fast a computer can think and act.

RAM: The chips which determine how many things a computer can think about at once.

hard drive: The disk which records all the things a computer might want to remember.

A computer's software capabilities depend on two things: the power of the hardware just mentioned and the computer's operating system (the way the hardware runs programs). As of the eve of Y2K, most software was created to run using one of the following operating systems:

DOS/Windows 95/Windows 98/Windows ME: Found on about 70% of computers.

Windows NT/Windows 2000: Found on about 20% of computers.

Macintosh OS: Found on about 5% of computers.

Unix/Linux: Found on about 5% of computers.

The overwhelming majority of software is made to work using Microsoft's Windows systems. Macintosh is popular among home users and graphics professionals. Unix/Linux is popular among computer programmers. The vast majority of these operation systems use graphic user interfaces (GUI, "gooey"). In other words, users move a cursor around the screen and click on icons to make things work. The alternative to GUI is typing (and remembering) text codes which trigger the same functions as GUI's mouse clicks.

In addition to core hardware and software, computers can be given expanded functionality with hardware add-ons including:

printers: devices which transfer electronically designed documents to paper

digital scanners: devices which transfer paper documents or images into electronic documents

modems: devices which send signals between computers through telephone lines

network cards: chips which send signals between computers through special routers

Other items (less important to the discussion here) include digital cameras, joysticks, audio speakers, fax connections, and mouses. (The plural of the point-and-click device is mouses; the plural of the quick little animal is mice.)

The critical add-on when talking about the Internet is modem speed which determines how quickly a computer can send and receive information. Modems transmit data very slowly (text moves about 2,000 characters a second, but images take longer, audio longer still and video is almost impossible). From 2000 to 2010, all Internet access will move to broadband formats (like DSL or cable modem) instead of the current phone line modems. Wireless Internet access may still suffer slowness.

The speed and power of a computer's hardware, software and modem speed combine to determine the most important factor of a user's experience: time.

Non-computer wired appliances include cell phones, Palm Pilots, video game systems, portable MP3 players, and WebTV. Unusual wired appliance include microwaves (scan prepak meal's bar code, oven automatically sets time and warns about allergies) and refrigerators (yes, you can log in from work and see what you need to pick up on the way home).

File extensions

Just as processors, RAM, and hard drives make up the realm of "hardware," more immediate to users in most cases is the realm of "software" - program which actually allow people to do something with their computers. Ever since Bill Gates made up the rules in early versions of DOS, the purposes for inidividual computer files have typically been noted with a dot and two or three characters at the end of file names. These dot and character additions are called file extentions.

For example, the purpose for a file labelled "junltr" was made more clear to users and machines by adding ".doc" to it, thus meaning "junltr.doc" was a word processing document to be run within the Microsoft Word application program.

Recognizing these sorts of common file extentions becomes second natures to interactive designers. There following examples are common on computers running a version of Windows:

.txt (plain text files)
.exe (DOS- or Windows-executable files, also called applications)
.psd (Photoshop image files)
.doc (Microsoft Word files)
.xls (Microsoft Excel spreadsheets)
.fla (raw Macromedia Flash files)

The most common file types encountered online include:

.txt (plain text files)
.htm, .html (simple Web pages)
.cfm (ColdFusion database Web pages)
.asp (Active Server Page scripts or Web pages)
.stm, .shtml (dynamic or server include Web pages)
.gif (images made faster using GIF compression format)
.jpg, .jpeg (images made faster using JPEG compression format)
.mp3 (audio files made smaller using MP3 compression format)
.wav (audio files made smaller using WAV compression format)
.mov, .qt (video files made smaller using QuickTime compression format)
.rm, .ram (video files related to RealVideo/RealAudio compression formats)
.swf (finalized Macromedia Flash movie files)
.zip (a file or directory compressed into a smaller, tighter archive format)
.hqx, .sit (a file or directory compressed into an archive format mainly for Macintosh users)
.pl (a server script written in Perl, a scripting language)

A note of warning: Sometimes these file extentions are hidden from the day-to-day user. Older versions of Macintosh hide extentions and ignore file names; UNIX systems typically get no special meaning from extentions. Even Windows itself has settings allowing users to turn off seeing file extentions. As with everything online, this rule of thumb is a guideline, not a law.