How to make computers work from a different continent?

If I buy a computer from a different continent then would I need to buy a device, for the computer to work in my continent?

I live in America.

I don't see a power cable that I can buy with the computer that I am interested in buying. Can I use a universal power adapter with the computer?
Update: I was looking at some forums that discuss about my question. A plug converter, and a voltage converter, or power converter is what I don't have, and I think I might have to buy it.
Update 2: I already know about the PSUs switch, for desktops, so maybe I just have to buy a plug converter.

Regarding the power adapter, I don't know if I should use a universal power adapter, or if I have to look, for a power adapter that specifically works with the computer, and will work in America.
Update 3: I figured it out. I will be buying the power adapter from the other continent, and plug converter, and voltage, or power converter, and that's if I buy a desktop that can switch voltages.
Update 4: I figured it out. I will be buying the power adapter from the other continent, and plug converter, and voltage, or power converter, and that's if I buy a desktop that can't switch voltages.
Update 5: The plug converter should allow me to plug in the power adapter from the other continent in my outlet, or power bar, but I think the difference of voltages still is a problem. I am going to buy a voltage converter, and use it just to make sure nothing bad happens to my computer.
Update 6: If I buy a laptop then I am going to buy a voltage converter.
Update 7: If I decide to buy a desktop, and it doesn't have a switch to change the voltages then I will buy a voltage converter. I don't know if all desktops have that switch.
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