Internal Parts of a Computer

By Ma Wen Jie

Updated September 15, 2017

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Modern PCs are made of a series of interconnected devices and sub-systems. Understanding these systems will help to troubleshoot computer failures or performance issues. Although there have been many advances in microcomputer technology, the basic architecture of a personal computer has remained relatively constant since the introduction of the first personal computers.


All computers are built around a mainboard, which contains all of the connectors that allow the various other subsystems to interact. CPUs and random access memory (RAM) mount in sockets on the main board while other subsystems are connected via cables or built on cards that mount directly on the mainboard.


The central processing unit (CPU) is the component that performs all calculations and mathematical manipulations in a computer. CPUs are sometimes single-chip devices and sometimes are packaged together with supporting circuits like memory and buffers mounted on a board, and packaged together in a single unit.


RAM is the memory that computers use to store data and instructions needed by the CPU for computer operation. RAM generally consists of memory chips and control circuitry mounted on a circuit board with pins that slip into RAM slots on the main board. In situations where a computer needs more RAM than is physically available, computers use a hard drive for additional storage. Using a hard drive for temporary memory usually has a negative effect on computer performance and is an indication that a computer needs more memory.

Disk Drives

A computer contains at least one disk drive. There are several types of drives, including CD or DVD drives, floppy disk drives and hard disk drives. A hard disk drive is usually the main storage drive on the computer, and stores data and programs that are loaded into RAM for use. Some modern hard disk drives use large quantities of solid state memory and contain no moving parts, however most are made of multiple disk platters that spin at a high rate of speed to allow for faster data transfer.

Interface Cards

Most computers allow for a variety of interface cards, which allow external devices to input or read data from the computer. Examples of interface cards include video cards, audio cards, network cards and modems. Modems are cards that allow data communication over standard telephone lines. In many cases, a single interface card allows many devices to be used on a single computer. A good example is a USB card, which allows many devices to send and receive data from a computer. In the past, USB was implemented only on an interface card, but many modern computers implement USB on the main board, thus negating the need for a card.

Power Supply

All computers require a power supply, which provides even, constant power to the main board and to other components, like disk drives. Power to interface cards or devices connected directly to the main board pass through the main board before being delivered to the card or device.