Viruses
Viruses can corrupt or destroy the information and data stored in your computer, including the system software needed to run your computer. They can duplicate themselves and spread to other computers.
Example If you have a virus on your hard disk, and you copy data from your hard disk onto a floppy disk, the virus will copy itself across as well. There are now two copies of the virus, one on your hard disk and one on your floppy disk. When you put the floppy disk into another computer, the virus will copy itself onto that computer. There are now three copies of the virus - one on your computer, one on a floppy disk, and one on another computer. Any floppy disk that goes into an infected computer comes out with a copy of the virus on it. Any computer that an infected floppy disk goes into becomes infected with a copy of the virus. Viruses spread very rapidly this way.
Viruses can enter your computer every time you put data into the computer from a disk, the Internet, a modem or a network. The only "safe" computer is one with no disk drives, no hard disk, no network and no modem.
Floppy Disks out of a packet are not safe. They could have been programmed with a virus when they were made.
Protection against Viruses
The only way to protect your computer from viruses is to immunise it.
This involves having anti-virus software installed and running. The anti-virus software should check for viruses whenever the computer is turned on, whenever a floppy disk is put in the disk drive, and whenever you connect to another computer through a modem, the Internet and a network.
The anti-virus software should be updated regularly (e.g. every month) as new viruses are being discovered all the time.