Understanding how the many parts of a computer connect to each other inside your PC begins with the case, which physically houses most of the components.
You might need to know how the inside of your computer works when upgrading or replacing hardware, reseating devices, or just out of curiosity.
Inside the Case

Power Supply: The power supply connects to nearly every device in the PC to provide power. It is located at the rear of the case.
Drive Bays: The 5.25″ and 3.5″ drive bays house the many kinds of storage devices a computer might contain.
Expansion Slots: The expansion slots at the rear of the case are specially cut out so the peripherals connected to the motherboard can extend from the case for easy connection to external devices such as printers, monitors, and other external devices.
The Motherboard
The motherboard is mounted inside the computer case and is securely attached via small screws through pre-drilled holes. All of the components in a computer connect to the motherboard in one way or another.
- Expansion Cards: Motherboards usually contain a number of slots for internal peripheral cards like video cards and sound cards to connect to.
- Back Panel Connectors: The back panel connectors extend out the back of the case for connection to external peripherals.
- CPU & Memory Sockets: The CPU and memory connect directly to the motherboard via the CPU socket connector and memory slots.
- Storage Drive Connectors: Storage devices are connected via cables to the motherboard. There are special connectors for floppy drives, optical drives, and hard drives.
Storage Devices
Storage drives such as hard drives, optical drives and floppy drives all connect to the motherboard via cables and are mounted inside the computer.
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info taken from LifeWire.com