Windows Computer System Overview

This topic will describe the hardware, operating system, and hardware drivers which make your personal computer work. The below diagram shows all the computer component functional blocks that we will discuss. Our relate topic computer troubleshooting will use these functional block descriptions to help you find out what is wrong with your computer.

This page is designed with a separate window for viewing the above functional block diagram while reading the descriptions below. When this new window opens, adjust it's size as required, and then use alt-tab keys to switch back and forth between the text window and the diagram window. To open functional block diagram, click Computer System Block Diagram.

Major Computer Components

As shown in the block diagram, there is a user, a computer case, an operating system, and computer applications (bottom to top). The purple boxes contain hardware components outside of the computer case. The white boxes are hardware and operating system drivers which the user can not normally change. The yellow boxes are hardware and operating system drivers which the user can replace.

The light blue boxes are applications which the user can start or stop. The green boxes are the windows operating system components which enable the computer system to function.

Computer Case Hardware Description

CPU & Memory - We will start out with the CPU & Memory hardware. You can compare the CPU (central processing unit) to someone who is very stupid, but is also very fast. That person can only do precisely what they are told to do, but they can do each task very fast. While performing these very fast tasks, they must store user input and user output, in addition to temporary storage of calculations that they do. The memory is where the CPU stores things, including the next thing it is to do. Since it may be doing something else while the user is typing, the CPU has to store the typed keys in memory until it gets around to responding to the type keys. Because the CPU is very fast, it can do hundreds of millions of things each second, so it appears to the user that the CPU is always ready to receive keyboard commands and mouse actions.

BIOS - The BIOS stands for "basic input output system". We said earlier that the CPU is very stupid. The BIOS is what tells the CPU what to do when it is first powered up. The BIOS has another important purpose, and that is to map out where all the computer hardware parts are located. Each computer manufacturer uses electronic components to build the computer. Which components and how they are connected is not known by the people who developed the computer operating system. So the BIOS serves as a guide and reports to the operating system where all the hardware components are located. It is sort of like a road map which reports the location of the computer hardware.

When the computer first starts up, the BIOS does some diagnostic tests to see if everything looks OK. Then it tries to find an operating system on a disc drive. If it finds an operating system, then it loads the first part of this operating system, and then runs out of smarts, so the BIOS lets the first part of the operating system load in the rest of the operating system from the disc drive. Once the operating system has self loaded itself, it then does some housekeeping, and then it displays the desktop display on your video monitor. The operating system is now fully loaded and ready to serve your needs.

Computer Ports - The motherboard speaker, the floppy disk drive, and the printer are driven by ports. These ports are just connections so that the devices can be connected to the computer. The motherboard speaker can beep out codes when the BIOS finds errors during that diagnostic test we mentioned earlier. Some older applications also used the motherboard speaker with limited success. The printer port is called a parallel port and is what is used by most printers today. Some of the newer computers have a new port called a USB port. This is a serial port which has become very popular recently, because it is hundreds of times faster than the older serial ports. The modem in this computer emulates both a serial port and the modem.

IDE Bus - A computer bus is a special connection which connects the CPU to various hardware cards. The IDE bus is the most common bus today which connects disc drives to the CPU & Memory. The IDE bus also has drivers so that the operating system understands how to talk to the IDE disc drives.

Adapters - The video adapter and the sound adapter are usually removable cards which can be changed. Some of the newer computer motherboards have included these adapter functions so that the physical adapter cards are not necessary. When this is the case, the BIOS for that motherboard informs the operating system so that the virtual adapters function just like a physical adapter would have. The operating system doesn't care about the switch.

Windows Operating System - The operating system is very complex so that it is very easy for you the user to control the computer. Yeah, right! Really though, the operating system takes care of millions of details to make your life easier. For example, the BIOS told the operating system where the printer port is located, but even the BIOS doesn't know what type of printer you have connected. Therefore, you the user have to tell the computer what type of printer you have on your printer port when you set up the computer for the very first time, or when you later change the printer type.

Remember earlier when we said that the CPU was very fast but very stupid. The operating system tells the CPU what to do after the operating system has loaded. But even the operating system doesn't know how to talk to your printer because each company used different electronic parts and connected them in different ways to build each printer.

Drivers - The solution to this problem was in drivers. No we dont mean truck drivers either! These drivers are computer programs written by the hardware manufacturer (in this example, printers) which explain to the operating system just how to talk to that hardware device (in this example, printers). Everytime you add new hardware to the computer, you must also install a new hardware driver so the operating system is told how to talk with that new device.

In the drawing you will see white drivers and yellow drivers. The white drivers are setup by the operating system and the user has little if any control over these drivers. The yellow drivers on the other hand, can be added and removed by the user as the associated hardware is changed by the user. The color yellow was used to mean that yoou should use caution because the operating system will let you mess these drivers up. Typically when some hardware device quits working, it is because the associated driver has been deleted or corrupted. When this happens, you can locate the manufacturer's driver and reinstall it to fix the problem.

The Memory Manager is also a driver. It keeps track of how the memory is used by both the CPU and the applications. The BIOS tells the memory manager where the memory is located, but the Memory Manager controls who gets to use the memory.

The Print Spooler Driver is a virtual location in memory where stuff going to the printer can be stored until the printer gets around to taking the print data. The Print Spooler passes data to the printer driver who knows how to talk to the printer and keep the printer happy.

The Network Driver is how you connect to the internet. Networking simply means connecting computers together. The Network Driver allows your operating system to connect with the operating system of another computer. The Nework Driver understands the connectivity and also aacts as traffic cop to ensure that the two computers pass error free data back and forth. If there is an error, the network driver demands that the data be resent until it is without error. The operating system does not know about the repeated error data, the operating system only sees error free data from the remote computer.

Applications - Applications are simply computer programs which are designed to do a certain task or job. Applications are normally started and stopped by the user as required. We have listed some typical applications that internet surfers use. Please note that the desktop application is a bridge between applications and the operating system. The desktop is where you start and stop all your other applications. When the computer starts up, the first application to start is the desktop, and the last application to shut down during computer shutdown is the desktop. WIthout the windows desktop, the user is helpless.

This completes the overview of a windows personal computer. Other topics will expand each area to provide understanding beyond this basic understanding. Good luck, and learn all you can in life.

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