How Does a Computer Work?

The tower is laid on its side the way a technician works on it, so most parts lift straight up (+z). The two drives and the power supply slide out sideways along their bays: the drive out the front (+y), the PSU and rear fan out the back (−y). Unplug the PC before step 1. The order is a real teardown, from the side panel down to the bare motherboard.

1. 1Side panelCovers the open side of the case and keeps dust out and airflow on its intended path.
2. 2Graphics card (GPU)Turns numbers describing an image into the pixel colours sent to the monitor.
3. 3CPU cooler (heatsink + fan)Draws heat away from the processor so it can keep running at full speed without damaging itself.
4. 4Processor (CPU)Fetches each instruction from memory, decodes it and executes it, one step after another, billions of times a second.
5. 5Memory (RAM, two sticks)Holds the bytes of the programs and data in use right now, each one at a numbered address.
6. 6M.2 solid-state driveKeeps the operating system and files permanently, even with the power off, and loads them into RAM when needed.
7. 73.5-inch hard driveBulk long-term storage: large and cheap, but the slowest store of bytes in the machine.
8. 8Power supply (PSU)Converts mains AC electricity into the steady low DC voltages every other part runs on.
9. 9Rear case fanPushes warm air out of the back of the case so fresh air can be drawn in at the front.
10. 10MotherboardConnects every part with copper traces (the buses) that carry bytes and power between them.
11. 11Case chassis (tray)The rigid steel frame that everything screws to and that shields the electronics.