Question

why do we need to keep magnetic devices away from computer devices

Answer 1

There are two ways in which a magnet might harm a computer.

One is through loss of data on magnetic media. This includes traditional mechanical hard drives, floppy disks and any other magnetic storage media. These components are potentially vulnerable because they use magnetization as a means of recording data, but the magnetic forces are controlled. A strong magnetic field could wipe data by interacting with and changing the magnetization of the drive.

The second potential issue is a magnet’s field potential to generate a charge in objects around it.

Just as a wireless charger, an innovation that uses this fact to transmit power wirelessly over very short distances. It’s possible the same effect (if substantially amplified) could induce a charge in your computer’s electronics, frying them. Electromagnetic pulse weapons work on the same principle.