1.17 Filename Extensions
In DOS and some other file systems,
filenames often have the form
UNIX doesn't have any special rules about extensions. The dot has no special meaning as a separator, and extensions can be any length. However, a number of programs (especially compilers (52.8 ) ) do make use of one-character extensions to recognize some of the different types of files they work with. In addition, there are a number of conventions that users have sometimes adopted to make clear the contents of their files. (For example, you might name a text file containing some design notes notes.txt .)
Table 1.2 lists some of the extensions you might see to filenames, and a brief description of the programs that recognize them.
In Table 1.3 are some extensions that are often used by users to signal the contents of a file, but are not actually recognized by the programs themselves.