1. System Components Overview

2. The PC
External view of a complete, modern PC system. (Micron's New Millennia MAX)
External view of a complete, modern PC system. (Micron's New Millennia MAX)

3. The PC - Cont.
The main reason why the Personal Computer, also known as the Desktop PC platform has been very successful over time, even with the introduction of newer and more exciting technologies, is that it is made up of many any different individual components, which can be mixed and matched in thousands of different combinations.
This allows a user to customize the PC to meet their exact needs.
Today, we discuss the major components of a typical PC

4. System Case The box or outer shell that houses most of the computer,
While it may seem inconsequential, the case actually performs several important functions for your PC that include protection for the computer circuits from the external environment, cooling and system organization.
Also, the system case is normally purchased together with the power supply, both of which must be matched with the size, shape and electrical requirements of your motherboard. It therefore determines the available options depending on the use

5. Power
A computer is an electronic device therefore its many components require power to function. There are two aspects to power in the PC:
External Power: This is the power delivered to the back of the system case. There are several considerations regarding this power and how it is supplied that will determine if your internal power supply is going to work the way it should.
Power Supply: The power supply is the small box that sits inside your case and takes the external power you supply to the computer. Its main job is to transform this power into a form the rest of the computer can use

6. Motherboard and System Devices
The motherboard is the base of the modern computer system. It is amazing how little attention this critical component gets in mainstream circles, considering how much it does--though this situation is now improving, fortunately. If the processor is the "brain" of the computer, then the motherboard is the central nervous system and circulatory system, plus much more, all rolled into one. Here are the main parts of the motherboard and its related devices:

7. Motherboard
The motherboard is the main circuit board in the computer where everything comes together. This is where you plug in your processor, memory, cache, video card and other cards. It is also where you connect your peripherals.

8. System Chipset and Controllers
The chipset and other motherboard circuitry are the "smarts" of the motherboard. Their job is to direct traffic and control the flow of information inside the computer. These circuits control the processor's access to memory, the flow of data to and from peripheral devices and communications lines, and much more. The chipset is a critical part of any computer, because it plays a big role in determining what sorts of features the computer can support. For example, which processors you can use, which types of memory, how fast you can run the machine, and what kind of system buses your PC can use, are all tied in to the type of chipset the motherboard uses.

9. System Buses
The system buses are the electrical channels through which various parts of the computer communicate. The physical part of these buses, the part you see, is the set of slots in the back of the machine into which you put your video card, sound card and other cards. It is over the system buses that your video card gets information from the processor, the processor saves data to your hard disk, etc. The architecture chosen for each of the system buses has a great impact on the performance of your PC, as well as dictating your choices for video cards and other devices.

10. BIOS stands for Basic Input/Output System
pronounced "bye-oss" or "bye-ose")
This is a computer program that is built into the PC's hardware. It is the lowest-level program that runs on your computer. Its job is to act as an intermediary between your system hardware (the chipset, motherboard, processor and peripherals) and your system software (the operating system).
By doing this, the operating system doesn't have to be made different for every machine, which is why DOS will load on any PC. The BIOS is what runs when you turn on your computer, and what loads your operating system (for example, DOS)
The BIOS also allows you to set or change many different parameters that control how your computer will function

11. Cache
The system cache is a small, high-speed memory area that is placed between the processor and the system memory. The value of the cache is that it is much faster than normal system memory. Each time the processor requests a piece of data from the memory, the system first checks the cache to see if the information is there. If it is, then the value is read from cache instead of memory, and the processor can get back to work that much sooner. If it isn't, then the data is read from memory and given to the processor, but it is also placed into the cache in case the processor needs it again in the near future.

12. System Resources System resources are not actual physical devices
First, they dictate how your PC organizes its access to various memory areas and devices.
Second, they are one of the most common areas where people have PC setup problems or resource conflicts.
These are the four types of resources that various parts of your computer can sometimes decide to fight over:
Interrupts (IRQs)
Direct Memory Access (DMA) Channels
Input/Output (I/O) Addresses
Memory Addresses

13. The Processor Also the CPU or Central Processing Unit
reffered to as the "brain" of the computer. An extremely sophisticated piece of miniaturized electronics.
The processor reads instructions (commands) from memory that tell it what it needs to do to accomplish the work that the user wants, and then executes them.

14. System Memory Also called RAM, which is the Random Access Memory
holds all of the "active" information that the computer is using.
When you turn the computer on the memory is empty.
Each program or data file you load uses part of the system memory.
When you close a program the memory is freed up for other uses.
General rule of thumb, the more memory your system has, the more things you can do with it simultaneously.

15. Hard Disk
The computer's main "long term memory"--it holds your operating system, programs and data files.
Hard drives are the fastest form of long-term storage your computer uses.
They have currently increased in size and speed to values unheard of just a few years ago.

16. Floppy Disk Drives
The computer's smallest and slowest form of long-term storage.
Floppy disks provide a simple, convenient way to transfer information, install new software, and back up small amounts of files.
Floppy disks are universal: virtually 100% of PCs made in the last 10 years use a standard 1.44 MB floppy drive.

17. CD-ROM Drives CD-ROM stands for Compact Disk - Read Only Memory
CD-ROM drives use compact disks, similar to the ones that hold music, to hold computer information.
And also as the name implies, they are a read-only medium. You can read information from them but not write to them (except for some special exceptions).
CD-ROMs are a popular way that computer companies distribute applications and games, and are ideal for multimedia information like videos, music and large graphics files.

18. Peripheral I/O
Peripherals are external devices that you connect to your PC. (Well, technically your hard drive and CD-ROM etc. are peripherals too, but often people use the term to refer to devices outside the main box). There are two main ways that you can connect peripherals to your machine: through a serial connection, or through a parallel connection:
Serial Communications: A serial connection sends information over the line one bit at a time. It is a simple way to send information in or out of the computer, but is not as fast as other ways the computer can communicate. Serial connections are typically used for devices such as mice and modems.
Parallel Communications: A parallel connection is faster than a serial one because it sends many bits in parallel. The advantage of this is that it is faster, but the disadvantage is that it is more complicated to do. Parallel connections are used most often for printers and removable storage drives, which need more speed than serial peripherals.

19. Video Cards
Your video card performs the function of displaying the screen you see on the monitor. Inside the video card is a special kind of memory called video memory, where information is stored that represents what you see on the screen. If you look closely at the screen you can see that it is made up of many dots, or pixels. Each pixel's color and brightness is stored in the video memory.
When the computer wants to display something, it calculates how it needs to change the color and brightness of the different pixels, and changes the values in the video memory. The video card then presents the new pixels to you on the monitor. In modern computers, this calculating job is shared between the processor and the video card itself. Having the video card do the calculation can often be much faster, because the video card is specialized to do these types of calculations. Also, while the video card is doing this work, the processor can go on to other things.

20. Monitors
In simple terms, the monitor, sometimes also called a CRT after the main technology used in making them, is a specialized, high-resolution screen, similar to a high-quality television. Many times per second, your video card sends the contents of its video memory out to your monitor. The screen is made up of a matrix of red, green and blue dots. The information your video card sends controls which dots are lit up and how bright they are, which determines the picture you see.

21. Keyboards
the main input device for most computers. It is used to input textual information to the PC. Keyboards are pretty much standard affairs these days, although they can vary greatly in quality and appearance, and some have significant additional features.

22. Mouse
Until the invention of graphical operating systems, the keyboard was the only way that most people input information into their PCs.
Mice are used in graphical environments to let users provide simple "point and click" instructions.
The main advantage of a mouse over the keyboard is simplicity.
There are also some operations that are much easier to perform with a mouse than a keyboard (such as picking an item on a screen or choosing from a list of options).