filenames can be up to 255 characters long, but some older systems only allow 14 characters. When naming files, try to pick filenames that are concise, yet meaningful to you. When you have not used a file for a while, it's helpful to have a name that reminds you of what's in the file. Because UNIX is case-sensitive, another good idea would be to always use lower case when naming files and directories. Easier to remember.

Conventionally, a lot of computing filenames have an extension composed of the period and a descriptive character or characters. For example, C-language programs must be named a name whose last two characters are .c. Note that this is not really an extension; it's just that the last two characters of the filename are . and c. Pascal programs may be named ending in .pas or .p . Fortran programs must end in .f