It is true, as reported in "The Software Free Lunch" (Executive Micro, June), that many excellent programs exist in the public domain. However, micro users who are enthused about getting a free "byte to eat" should be cautious.

Demented practical jokers spend hours writing "Trojan horse" software that they slip into the public domain posed as useful programs. In fact, these programs erase or scramble data and file-allocation tables on the floppy and/or hard disk.

Have someone vouch for unknown public-domain programs before you run them. Use DEBUG to examine the ASCII strings. Watch for DISK CALL codes (interrupt 13H). Back up all data before experimenting with unknown programs. Use trash or write-protected diskettes in floppy mode.