Final answer:
Unix and Windows 2000 are examples of multi-tasking operating systems that allow multiple tasks or programs to run simultaneously.
Step-by-step explanation:
Unix and Windows 2000 are examples of multi-tasking operating systems. Multi-tasking operating systems allow multiple tasks or programs to run simultaneously, sharing the resources of the computer. They enable users to switch between different tasks, such as using a word processing program while listening to music or browsing the internet.