The official motherboard definition is that it's the main printed circuit board within a computer, which means it's the primary piece of circuitry that all of the other pieces plug into to create a cohesive whole.
A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load.
Random-access memory is a form of computer memory that can be read and changed in any order, typically used to store working data and machine code.
A central processing unit, also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, and input/output operations specified by the instructions in the program.
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