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
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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