1.1.7 internal Components

The power supply is the big square component that converts AC power from the wall into DC power that the computer can use.
This conversion is from AC to DC, represented as $\text{AC} \rightarrow \text{DC}$ .
It provides power to all internal components of the computer.

The CPU sits under the CPU fan and heat sink, which are located directly on top of the CPU.
CPUs generate a lot of heat; the CPU fan and heat sink pull heat away from the CPU and dissipate it, cooling the CPU.
Without this cooling, the CPU would overheat.
If the heat sink is removed, the CPU is exposed (the transcript notes it as a metallic square).

Everything in the computer, including the CPU, is connected to the motherboard.
The motherboard is the component at the bottom of the case that connects all parts together.
It is described as the heart of the computer.
It contains all wiring and circuitry necessary for the different components to communicate with each other.

Memory modules, or RAM, are inserted into memory slots on the motherboard.
This is where data that the CPU is currently working on is stored.
RAM represents short-term storage; when the power is turned off, the data in these modules is erased (volatile memory).

Hard disk drives store data long-term.
HDDs can be identified by their size, appearance, and the cables used to connect them to the motherboard.
Most hard disk drives use a SATA cable (data cable) to connect to the motherboard.

An optical disk drive is another storage device; the transcript references a DVD ROM drive.
Optical drives are larger than hard disk drives and typically use an IDE cable to connect to the motherboard.
Some newer optical drives use SATA cables instead.
Like the HDD, optical drives have two cables: one to the motherboard (data) and one to the power supply (power).
The transcript notes the back end of the optical drive as part of identifying it.

An expansion card is the card sticking out of the motherboard; it is inserted into the motherboard's expansion slots.
Expansion cards customize a computer to perform a desired function.
Example given: a high-end graphics card, which enables the computer to play the latest PC games.
Other types of expansion cards include audio expansion cards and networking expansion cards.

These are the key internal components of a desktop computer: power supply, CPU and cooling (CPU fan and heat sink), motherboard, RAM, HDD, optical drive, and expansion cards.
Cables are essential for operation: storage devices typically require two cables (data and power). For HDDs, the data cable is usually SATA; for older optical drives, IDE may be used, though newer drives may also use SATA.
RAM provides volatile, short-term storage for data the CPU is actively using; HDDs and optical drives provide long-term and removable storage options.
The motherboard serves as the central communication backbone, connecting CPU, memory, storage, and expansion cards.
As a PC technician, you should be able to open any computer system and immediately identify these components.