File Names

A little history

When the IBM PC was first invented, names of files were allocated a limited number of bytes on a storage disk. To be precise, twelve bytes were allocated. Eight for the individual user-generated name of the file, one for a full stop and the remaining three for an extension. The extension tells the computer what sort of a file it is.

Extensions

Although the size restrictions on the lengths of file names has been removed, most extensions still observe the three character limit. This page is devoted to listing a number of extensions that you will come across.

Program extensions

.exe

This is the usual type of program

.com

These aare also programs, but are not met so much these days

.bat

These programs shouldn't exist. they are a hangover from the days of DOS.

.dll

'.dll's are dynamic linked libraries. That means they are bits of programs which can be shared by other programs.

Document formats.

.txt

The text format used by windows Notepad and other text editors. The only formatting in a text file is 'new line' and 'carriage return': produced by pressing thr 'enter' key.

.rtf

The 'rich text format', used by windows Wordpad (found in accessories)

.doc

This format is used by Microsoft Office Word Processor, but because of continuous development such documents may be incompatible with each other

.pdf

The portable document format invented by adobe

Picture formats

.bmp

This is a lossless format and, therefore, produces very large files.

,jpg

This is a compressed format, usually used for phorographs.

.gif

This is a compreesed format, usually used for line drawings and cartoons.

.png

A newish format intended to replace '.gif's

Others

There are probably ten to twenty other formats, but the above four cover most images.

Internet files

.htm or .html

These are text files embelished with tex instructions to the web browser to control the overall appearance of the web page.

.css

Cascading style sheets are text files which control the style of the web page.

.js

Javascript files are text files which add automation ans interaction to web pages.

These are just a few of the very many many extensions used. To see more click here.