Configuration

Exploded view of a modern personal computer: 

1. Display 

2. Motherboard 

3. CPU (Microprocessor) 

4. Primary storage (RAM) 

5. Expansion cards 

6. Power supply 

7. Optical disc drive 

8. Secondary storage (HD) 

9. Keyboard 

10. Mouse Personal computers can be categorized by size and portability: 

• Desktop computers 

• Laptop or notebooks 

• Personal digital assistants (PDAs) 

• Portable computers 

• Tablet computers 

• Wearable computers 

Most personal computers are standardized to the point that purchased software is expected to run with little or no customization for the particular computer. Many PCs are also userupgradable, especially desktop and workstation class computers. Devices such as main memory, mass storage, even the motherboard and central processing unit may be easily replaced by an end user. This upgradeability is, however, not indefinite due to rapid changes in the personal computer industry. A PC that was considered top-of-the-line five or six years prior may be impractical to upgrade due to changes in industry standards. Such a computer usually must be totally replaced once it is no longer suitable for its purpose. This upgrade and replacement cycle is partially related to new releases of the primary mass-market operating system, which tends to drive the acquisition of new hardware and tends to obsolete previously serviceable hardware (see planned obsolescence). The hardware capabilities of personal computers can sometimes be extended by the addition of expansion cards connected via an expansion bus. Some standard peripheral buses often used for adding expansion cards in personal computers as of 2005 are PCI, AGP (a high-speed PCI bus dedicated to graphics adapters), and PCI Express. Most personal computers as of 2005 have multiple physical PCI expansion slots. Many also include an AGP bus and expansion slot or a PCI Express bus and one or more expansion slots, but few PCs contain both buses.