Do you need to buy a operating system?

Well, you will need an operating system. Without it your new PC is just a bucket of electronics. But, like others said here, you don’t have to buy an OS. If you decide on a commercial, proprietery OS (Windows) you’ll have to buy it.

Can I buy a computer without an operating system?

Few, if any, computer manufacturers offer systems packaged without an operating system (OS) installed. However, consumers who wish to install their own operating system on a new computer have several different options. … Another possible option is to purchase what is called a “barebones” system.