When RAM runs low, the operating system uses a virtual memory manager program to temporarily store data on the hard disk like it was in RAM, which makes RAM free for data manipulation. A virus is a computer program written to interrupt or destroy your work. A protocol for daisy chaining up to seven video devices together and connecting them to a single serial port. You will see this term appear before various computer terms to indicate simulation technology that enables you to cross boundaries and experience something without needing it's physical presence, as in virtual sex, and virtual theme parks. A virus can wipe out information on your computer and create major havoc.
Viruses usually originate from malicious people.
You can unintentionally download virus from a web site or get it from a disk that someone has lent you. There are virus-checking programs, but there are new viruses popping up every day. So the best defense against a virus is to be very careful not to download programs or data from a site you're not familiar with. A main-frame OS, designed for multiple users. While a similar concept to UNIX, the commands, applications, etc. are all very different.