The /etc/profile file is the source of your system wide defaults used by Bourne and related shells, this file in Slackware-current includes:
- Assignment of global variables such as MINICOM, MANPATH and HOSTNAM
- assignement of the proper .inputrc file
- User PATH assignments
- default shell prompts by user type
- default umask (it is recommended not to change this)
- mail notification
- additional directories to add to the
These default values are important to your system in in most cases these will not need to be modified, but in some cases you may want to add additional variable declarations, make some assignments conditional rather than static or add custom aliases to be defined for all users.
There are many different things you can add like company information, system identifiers or hardware information that can be tied into other scripts or be used by the users to intelligently speak with IT about the specific system(s).
I will not give examples because I am sure that you know what you want to accomplish and with sufficient knowledge of Bourne and related shells modification of this file should be quite simple.
I know this wasn't as informative as my other posts, but once you view your /etc/profile file you should understand how modifications can be useful to you.