A dongle (which is made for a serial
, parallel, usb, or other specific port) usually contains a crypto chip. When the computer queries that chip, the chip returns a specific code. No dongle? No code and the software doesn't run. Some vendors will sell you extra dongles so you can use the software on other computers--for a stiff license
fee. If it breaks or gets lost
, again, replaced with a stiff license
The sad thing is that there are often pirated versions of software that avoid dongles, they just stop honest people from straying.