Shareware, free ware, and public domain software are all a kind of non-commercial software usually distributed through electronic bulletin board services. Shareware cost something-but less then commercial software packages-and free ware and public domain software usually cost nothing.
Shareware is distributed on request for an evaluation period, after which a user pay a registration fee or returns the software. After user pay the registration fee or the licensing fee-he or she is usually sent documentation and in some cases, additional support and notification of updates.
Free ware author do not change their software, but they may limit its distribution. Sometime these authors ask for feedback from user regarding any bugs in and incompatibilities with the program.
Public domain software is entirely in the public domain-that is, it caries no copyrights-and carried no restrictions. User who use public domain software should keep in mind that software reliability may be an issue. It may have been copied many times and have been altered or tampered with in the process. Also, it may have a virus. User should install a virus-protection program on their computers and scan all shareware, free ware, and public domain disks before using the programs on that disk.