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Transcript of Comprehensive Computer Safety Training for OCES...
Comprehensive Computer Safety Training for OCES Employees Module 1 – Basic Computer Knowledge
Basic Computer Knowledge Page 2
Welcome to DASNR Technical Support and Services’ comprehensive safety training
material. As you progress through this material, you will learn a great deal about how to
use computers safely, both from the perspective of physical safety and of data security.
Each module covers a different area of computer use, and each module is broken down
into sections that can be covered at your own pace. At the end of each module are
practice quizzes to help you make sure that you’ve grasped the material. To receive credit
for this material, you’ll need to take the tests online.
If you would like to have one or more of the modules presented at your office or in your
district by TSS training and support staff, please contact your specialist to arrange this.
We’d be happy to oblige and can arrange for a class session to cover the material with a
test at the end to measure achievement.
All material herein is copyright Oklahoma State University unless otherwise credited.
Permission is given to reproduce this material for educational use, with the following
conditions:
1) The material may not be altered in any way, including titles, format and this
notice.
2) Credit must be given to Oklahoma State University for the material.
Basic Computer Knowledge Page 3
Contents Section I: Parts of a computer ............................................................................................. 5
Physical parts of the system ............................................................................................ 5
1. Power supply .................................................................................................... 7
2. Motherboard ..................................................................................................... 7
3. Processor ........................................................................................................... 7
4. RAM ................................................................................................................. 8
5. Hard Drive ........................................................................................................ 8
6. Floppy drive/Zip Drive ..................................................................................... 8
7. Optical drive ..................................................................................................... 8
8. Card slots .......................................................................................................... 8
9. Ports .................................................................................................................. 9
a) USB Ports ......................................................................................................... 9
b) PS/2 keyboard/mouse ..................................................................................... 10
c) VGA Video ..................................................................................................... 10
d) DVI Video ...................................................................................................... 11
e) HDMI Video ................................................................................................... 11
f) DisplayPort ......................................................................................................... 12
g) S-Video ........................................................................................................... 12
h) Network jack ................................................................................................... 12
i) Serial port ........................................................................................................... 13
j) Parallel port ........................................................................................................ 13
k) Firewire/IEEE1394 ......................................................................................... 14
l) Audio out/speaker .............................................................................................. 14
m) Audio in/microphone ...................................................................................... 14
Software components of the system ............................................................................. 15
BIOS ......................................................................................................................... 16
Operating system ...................................................................................................... 16
Applications .............................................................................................................. 16
The OS and hardware................................................................................................ 16
Section II: Things that stop the computer from working .................................................. 17
Physical (hardware) damage ......................................................................................... 17
Power issues .............................................................................................................. 17
Heat ........................................................................................................................... 18
Basic Computer Knowledge Page 4
Liquids ...................................................................................................................... 19
Impact ....................................................................................................................... 19
Component Failure.................................................................................................... 20
Diagnosing component failures ................................................................................ 20
Software Damage .......................................................................................................... 20
Poorly written updates .............................................................................................. 21
Application Conflicts ................................................................................................ 21
Troubleshooting steps ............................................................................................... 21
Appendix I - Basic electrical theory. ............................................................................ 22
Appendix II – Computer Ports Quick Reference .......................................................... 24
Appendix III – Further reading ..................................................................................... 27
Electrical Theory ....................................................................................................... 27
Computer Theory ...................................................................................................... 27
Appendix IV – Quiz ...................................................................................................... 28
Works Cited ...................................................................................................................... 29
Basic Computer Knowledge Page 5
Section I: Parts of a computer
A computer system consists of two main parts, each of which is subdivided into other
sections as well. The two main parts are the physical parts of the system, and the software
which runs the computer. The physical parts are shown in the picture below:
Physical parts of the system
The case is the outside of the computer, which provides protection from damage and
interference. The case also serves to regulate and direct airflow for the purposes of
cooling. Cases vary from the plain and utilitarian to the wildly fantastic in design. (Look
up “case modding” on Wikipedia to see examples of this hobby.) When personal
computers were first being made, cases usually required tools to access, but most now
have some form of opening lever – although the removable panels are sometimes still
secured by screws.
Inside the case are the main components of the computer itself; at a minimum, these will
include a processor and memory, but (in personal computers) usually includes a power
supply, hard drive or other storage, removable media drives such as CD-ROM or DVD
drives, and various cards (such as network or video) to add functionality.
Outside the case are the monitor, keyboard/mouse, and such components as external
drives.
Obviously, for a laptop, all of these parts (with the exception of the power supply) are
contained in one unit.
Basic Computer Knowledge Page 6
Internal Case Diagram – Desktop PC
(Gustavb, 2006)
1. Power Supply
2. Motherboard
3. Processor
4. RAM
5. Hard Drive
6. Floppy Drive (not shown)
7. Optical (CD or DVD)-ROM drive
8. Card Slots
Basic Computer Knowledge Page 7
1. Power supply. The power supply serves as a transformer for the electrical
powers coming into the computer, turning 120 VAC wall power into the voltage
needed by the components inside, generally 12 volt and 5 volt. Power supplies are
rated in terms of watts, so you’ll see 350 watt supplies, 550 watt supplies and so
on. It’s very important that the power supply have sufficient wattage for all the
devices plugged into it. A computer purchased from a dealer should be fine as it
comes from the factory, but if you add several drives and cards to it, you may also
need to upgrade your power supply.
2. Motherboard. The motherboard is the main circuit board in the computer. It has
connections for all the other devices. Some devices get power through the
motherboard (processor, cards), while some get theirs directly from the power
supply (drives). The motherboard may also have connections (“ports”) for
external system components, such as keyboard, video, network and so on. If the
motherboard goes out, the computer will have serious issues and will generally be
unusable.
The motherboard also contains the chipset, which is a series of onboard devices
for carrying out certain tasks. Some of these may provide video output, for
example, while others control memory access or server to monitor attached
devices.
3. Processor. The processor (or CPU – Central Processing Unit) is the core of the
computer. The processor carries out all operations on the computer, from booting
up to running the operating system to running applications. Processor speed is
directly related to computer speed, that is, the faster the processor, the faster the
computer. In the past few years, many computers have gone to “multi-core”
processors, processors which are groups of two or more processors. This helps
avoid bottlenecks in processing by allowing simultaneous processing of data.
Imagine that your CPU is like a factory, assembling products. The products are
the output of the programs running, the workers on the assembly line are the
processors, the stockpile of raw materials is your hard drive and the workers who
bring the raw materials are the northbridge (a dedicated part of the CPU). When
an order comes in (you tell the computer to do something) first the northbridge
fetches the data from the stockpile and loads into the RAM, which is like an
elevator for carrying the data from the hard drive to the CPU. Then the workers
grab the data and begin to assemble it, in order as each piece comes out. If more
than one thing is being built at a time, one will be built first, and then the other.
Multiple cores behave like multiple assembly lines; while the first line is busy
with the first product, the second one starts on the second, and so on. The line
speed itself is the bus speed of the CPU; that is, it is how fast data can flow from
the RAM into the processor.
As can be seen from the explanation, another important thing to consider when
choosing a processor is bus speed, which is the speed of the data pathways that
Basic Computer Knowledge Page 8
carry data to the processor. A fast processor connected to a slow bus may be
slower than a mid-range processor connected to a mid-range bus, since the fast
processor spends more time waiting for data and less time processing. Note that
you can’t actually see the processor; processors run very hot, and so are covered
by heat sinks and often dedicated fans.
Processor speeds are measured in Hertz (cycles/second), although modern
processors are fast enough to measure their speeds in Giga-hertz, which is to say
billions of cycles/second. (GHz is the abbreviation commonly used for
Gigahertz.) Provided the chips you are comparing use the same architecture, the
faster rated chip will be faster. If we compare an Intel i7 chip at 2.2 GHz to one
at 3.4 GHz, the chip rated at 3.4 GHz will be faster. However, we cannot do the
same with chips that have different architecture; an AMD chip or an Atom can’t
be directly compared to the i7 chips, or to each other.
4. RAM. Random Access Memory is the other core component of the computer. In
order to process data, the CPU has to have a place to temporarily store things,
which is what the RAM is for. RAM is the other main thing that affects computer
speed; since everything a computer does has to be run through the RAM, the more
it has, the less time you spend waiting. “Virtual Memory”, in which the operating
system uses hard drive space like RAM is not as effective, because transferring
data in and out of RAM is around 1,000 times faster than doing so to or from a
drive.
5. Hard Drive. Storage memory on the computer is supplied by the hard drive. The
drive is broken into sectors for easier addressing; a particular set of sectors is used
to contain information about how the computer should start up. This section, the
Main Boot Record, has the basic info needed to tell the computer about its
hardware and how it should activate that hardware and begin running the
operating system. Hard drives are one of the components of the system that wear
out, as they contain moving parts. (New “flash drives” do not have moving parts
and are thus not susceptible to mechanical wear.)
6. Floppy drive/Zip Drive. This has been phased out on modern systems, as
floppies simply don’t hold enough data to be useful, but was once a key part of
computer systems. Zip drives, which used a proprietary 100 MB disk, are
occasionally still encountered on older machines. They are essentially obsolete.
7. Optical drive. CD and DVD drives are called “optical drives” since they use a
laser and lens arrangement to read data off of the CDs or DVDs. (Or to write data,
in the case of recordable media.) In general, drives come in CD-ROM, DVD-
ROM, CD-R/W, DVD-RW and now Blu-Ray DVD forms. The –ROM drives are
only capable of reading disks, not writing to them. The other important
characteristic is size: a CD holds about 650-750 MB of data, a DVD generally
holds about 4.7 GB, and a Blu-Ray disc generally holds about 25 GB of data per
layer, with two layers being the current standard.
8. Card slots. These slots allow the addition of cards to the system to add different
types of functionality; cards can provide video, audio, network, data transfer
interfaces or other things. Card slots come in several different types, and it’s
important to buy a card that fits your system. Most modern motherboards will
Basic Computer Knowledge Page 9
have a PCI-E 16x slot for a graphics card, and a varying number of PCI-E 1x and
PCI slots. Eventually, PCI-E, which stands for Peripheral Component
Interconnect Express, will entirely replace the older PCI (Peripheral Component
Interconnect) interface.
9. Ports. These are the connections that allow devices to be attached to the
computer, including displays, keyboards, external drives, cameras and so on.
a) USB Ports USB – the Universal Serial Bus – is a way of connecting external devices of many different types to the computer. USB was developed in the 1990s as a way of simplifying the process and the number of different connectors that existed for making connections. USB plugs are (generally) rectangular with an internal filler block which has the actual electrical connectors on it; there are actually six different types of USB plugs, named USB-A, USB-B, mini-A, mini-B, micro-A and micro-B.
(Duye, 2009)
Of these, A is the most common for larger devices, such as keyboards, headphones and mice; B is commonly used for printers and scanners, and the smaller plugs are generally used for cameras, cell phones and so forth.
Basic Computer Knowledge Page 10
b) PS/2 keyboard/mouse
(Rogers, 2004)
These ports date back to the 1980s, introduced with IBM’s PS/2 computer. They are still somewhat in use, although USB has generally replaced them. Starting in the 1990s they were color-coded, green for mouse, purple for keyboard. One disadvantage of PS/2 devices is that the system only checks for them at startup; if you connect a mouse while the computer is on, you will probably have to reboot to use it.
c) VGA Video
(Lithgow, 2006)
VGA (Video Graphics Array) is a video standard that was also introduced with the PS/2 computer line. It is being replaced by DVI and other more advanced graphics connectors, but is still very common.
Basic Computer Knowledge Page 11
d) DVI Video
(Mobius, 2006)
DVI (Digital Video Interface) was designed in the late 1990s to replace the older analog video standards that had existed, such as CGA, VGA and so on. The four main plugs used are DVI-I single and dual link, and DVI-D single and dual link. DVI-D only carries digital signals, while DVI-I carries both digital and analog signal, which allows use of older VGA monitors or other devices with an adapter. DVI-A is designed to only carry analog signal and is fairly rare.
e) HDMI Video
(Bautsch, 2006)
HDMI (High Definition Multimedia Interface) was adopted in 2002 as a replacement for analog video signal methods in consumer devices, such as
Basic Computer Knowledge Page 12
televisions, DVD players and so on. Some computer monitors and projectors use this interface for video. Like DVI, it allows for more information to be carried, which allows for better quality video, as well as carrying audio information over the same cable.
f) DisplayPort
(Abisys, 2008)
DisplayPort was designed by VESA in 2006; it is intended to replace VGA and HDMI in computer applications, although not to replace HDMI in consumer usage. It is a digital video interface that can be used for high-resolution video signals. Many of the newer computers in OCES have this type of video port.
g) S-Video
(Gh5046, 2008)
S-video (Separate Video) was developed by JVC in the 1980s. Some computers have these ports (either the 7-pin version pictured above or a more common 4-pin version) which were intended to allow the computer to connect to older televisions. As modern flat panel TVS replace the old tube models, this type of port has become more and more obsolete.
h) Network jack
Basic Computer Knowledge Page 13
The network jack on the back of the computer is almost certainly an Ethernet port, designed to take an RJ-45 plug. The design is similar, but not the same size as the standard telephone jack, which uses an RJ-11 plug.
i) Serial port
(Lithgow, 2006)
Serial ports have been in use since the first mini- and microcomputers were manufactured in the 1970s. The port seen above (9-pin, DB-9 connector) was popularized by IBM on its PC-AT personal computer, which was launched in 1984. Serial ports have been used for a number of different devices, including printers, GPS units, mice and dial-up modems. In the scientific and industrial world a number of machines could be connected to a computer with a serial connection. Serial connections were slow, often unreliable, and have generally been replaced by the USB standard.
j) Parallel port
(Lithgow, 2006)
Basic Computer Knowledge Page 14
Parallel ports were introduced in 1970 by Centronics with their Model 101 printer. The technology was quickly embraced by a number of printer and scanner manufacturers, but was not standardized; some devices used 25-pin connectors, others 37 or 50. (And each of these had multiple types of plug as well.) IBM began putting on them on PCs in 1981, and their use quickly spread to include attaching external floppy, Zip or CD-ROM drives to computers. Like the serial port, these are almost entirely useless now, except in legacy applications. USB has generally replaced them on newer computers.
k) Firewire/IEEE1394
(KoS, 2006)
Designed by Apple in the late 1980s and early 1990s, FireWire (also called IEEE 1394) was intended for high-speed data transfer, particularly in audio-visual applications. Although faster than USB 1.0, it was more expensive and did not achieve wide adoption. Mostly replaced by USB now.
l) Audio out/speaker m) Audio in/microphone
These ports are usually color-coded and come in three varieties. Computers may have all, some or none of these, and some computers combine two of the varieties, as in the example above. The speaker port (green) provides
Basic Computer Knowledge Page 15
audio signal to computer speakers or headphones. The plug is not capable of driving standard home stereo or PA system speakers without an external amplifier. The plug is (usually) 1/8 inch stereo. The microphone (pink) provides an audio in for a computer microphone; it is also usually 1/8” stereo. Line in (blue) is for connecting other audio line devices to the computer to record signal from them; this could, for example, be used to connect a tape deck in order to convert cassette tapes into digital sound files.
Software components of the system
The hardware of the computer serves to run the software, or the instructions that the
computer needs to operate. The instructions range from basic things such as “what to do
when the power button is pressed” to the most complex parts of the Graphical User
Interface (GUI, pronounced “gooey”). Software is typically divided into operating
systems, which run the computer, and programs or applications, which are the tools the
user uses to do work. The diagram below explains the relationship between the
components:
From the diagram, we can see that the OS is involved in almost every task the computer
performs; when we run an application, the OS tells the application how to behave, and
Basic Computer Knowledge Page 16
the application works though the OS to receive input and to display output. Printers,
drives, mice, keyboards – they all have to talk to the OS.
BIOS. When the computer is first started, the OS is not the first thing to run; the first
thing that runs is a basic set of instructions, called the BIOS (Basic Input/Output System).
(In some systems, BIOS has been replaced by EFI [Extensible Firmware Interface];
however, everyone still refers to it as BIOS.) The BIOS first identifies and initializes
hardware items such as video cards, disk drives and I/O devices such as keyboards. It
then examines its list of boot devices to see if one of them contains information about
starting the operating system. If it locates such information, it starts that process and then
hands over control to it; this is typically seen onscreen by the replacement of the initial
screen, which often contains a manufacturer’s logo, with a screen displaying an operating
system logo.
The BIOS is useful both in that it allows for an easy set of instructions for the basic
initialization of the computer, and that it allows a great deal of control over how the
computer starts and operates. From within the BIOS, it is possible to specify boot order,
set the system time, enable and disable devices attached to the computer and control
hardware efficiently.
It is generally possible to access the BIOS settings at startup by pressing a key (on Dells,
the F2 key) and then waiting. The system will come up into the BIOS settings and allow
changes to be made, which then must be saved before restarting. Upon restart, the new
settings will be applied.
Operating system. The operating system (or “OS”) is what actually runs the computer;
it controls the hardware, getting input from the keyboard and mouse, displays data
through the video device, controls how applications are installed, how they run, and
generally regulates the system.
The operating systems in use in OCES include:
1) Windows XP
2) Windows 7 Professional
3) Windows Vista (deprecated)
4) iOS 4 (iPads and iPhones)
5) Windows Mobile 6.1, Windows Mobile 6.5, Windows Mobile 7, Android 2.x and
3.x – all phone/tablet OSs.
OCES is currently working at getting all capable systems up to Windows 7. Windows 8 is
expected to be out in 2012, so it’s possible that some users will never use Windows 7.
Applications. Applications are the programs that run on the computer: generally they
are the things that the user uses the most. Outlook, Word, Internet Explorer, Adobe
Reader, iTunes, and Microsoft Security Essentials are examples of applications.
The OS and hardware. The OS and the hardware have an important relationship.
Neither one can function without the other. The OS requires hardware to run on; that is, it
has to have a place to keep its files (generally the hard drive) and RAM and a processor
Basic Computer Knowledge Page 17
in order to do anything. The OS tells the hardware and the applications how to act, and
they do it. For example, when you click the “Shutdown” button, the OS begins the
process of shutting down the computer, closing programs and then telling the computer
hardware to power down.
At startup, first the BIOS checks the hardware, initializes it, and tells it how to load the
OS, and then the OS takes over and handles the rest of the boot sequence. The BIOS is
usually where all hardware is detected, so that the OS knows if it has a DVD drive or a
CD drive, what size hard drive it has, what sort of video card it has and so on. Then the
OS can actually make use of these things, telling the video card how to display the
desktop, checking the keyboard for input, understanding what clicking means on the
mouse buttons as well as running applications that are specified to run at startup and
preparing to run any other applications as desired.
All software components of the computer use the RAM as a space in which to run; a
computer with no RAM will not boot at all. The BIOS uses it briefly and then stops when
booting has been handed over to the OS, but from then on, the OS and the applications
have to share the available RAM. As an application runs, the processor has to carry out
instructions in order for things to happen. This all takes place in the RAM, which is why
increasing the amount of RAM in a system is generally an easy way to make the system
faster. The OS keeps track of the location of each set of instructions by “addressing” the
RAM, which is to say that it assigns a number to each location in the RAM. It is then able
to place and locate information in the RAM. Different operating systems can address
different amounts of RAM: XP, (as well as Vista and Windows 7 in their 32-bit forms)
are generally limited to 4 GB or less, but Vista and Win7 64-bit can both address up to
192 GB of RAM. The amount is important, because if you have more physical RAM in a
system than the OS can address, the extra is simply unused.
Section II: Things that stop the computer from working
There are a number of things that can stop the computer from working the way it should;
as you might guess, these can be divided into hardware and software problems.
Physical (hardware) damage.
Physical damage to a computer can come through several sources, including power
issues, heat, liquids, and impact.
Power issues. Power issues can be caused by either a failing power supply or variations
in the current supplied to the computer from the wall. Power from the wall is delivered to
your computers power supply at the nominal US voltage of 115 volts; the power supply
then converts the voltage into the levels required by the computer. Generally, these are 12
volts, 5 volts and 3.3 volts. One of the 5-V (volt) lines is used as a standby line and
supplies power to the computer even when the computer is off, keeping elements of the
computer ready to be quickly turned on.
Basic Computer Knowledge Page 18
A failing power supply may produce several symptoms. One that is common is for one or
more of the circuits coming out of it to stop delivering correct voltage, or perhaps to stop
delivering voltage at all. This will generally show up when components of the computer
stop working. For example, if the power to the hard drive is no longer active, then the
computer will display a “No hard drive found” message when booting; if the CD drive is
affected, you may not notice until you try to read or write a CD. If the power to the
motherboard is not functioning, then the computer will generally not turn on at all. This
will also be the case if the power supply is completely dead – more testing is required to
determine which problem is causing the issue.
The other primary power issue is caused by voltage fluctuations in the current from the
wall, either going over-voltage (surges) or under-voltage (drops). Surges can vary from a
small increase caused by a problem at the power company to massive ones caused by
lightning strikes. Protection against surges is generally a surge protector, which guards
against over-voltage conditions. A good surge protector should protect against most
things (direct lightning strikes are not included!) and will keep your system from being
damaged by an over-voltage. Every computer should be plugged into one of these
whenever possible, and it’s generally worth getting a good one. It would be a shame to
have a $1500 computer destroyed because it was plugged into a $3 surge protector
instead of a $30 model.
Under-voltage is more insidious than over-voltage. That is, it won’t make sparks shoot
out the front of your machine or cause other spectacular failures. However, under-
voltage, particularly if it continues for long periods of time, will cause parts of your
system to fail, particularly those parts with electric motors. (The power supply fan, other
fans, hard drives and so on.) It takes more time, but will shorten the life of the machine,
often by quite a lot. Under-voltage can be helped (provided it’s not too serious) by
installing a conditioning UPS. A UPS (Uninterruptible Power Supply) is a battery backup
for your computer; the idea is that it gives you time to shut your computer off normally if
the power goes out. A conditioning UPS regulates the power that goes through it,
diverting over-voltage into charging the battery (or to ground) and supplying extra
voltage from its battery when an under-voltage condition occurs. This ensures that the
current supplied to your computer is nice and even and steady. It’s a good thing to have
one of these for any machine, particularly if the current in your building is given to
fluctuations. They can cost from $80 to several hundred dollars, but are generally worth
the investment.
Heat. Heat is one of the things that will kill a computer very quickly, if given the chance.
All of the components in a computer generate heat, which has to be gotten rid of in some
way. The fans in the computer serve this purpose. There are generally at least two: one on
the power supply, and one on the processor itself. (The processor generates a huge
amount of heat). Some cases also have another fan that serves to circulate air within the
case.
Basic Computer Knowledge Page 19
Heat has two effects on a computer: the first is to slow it down. As electrical components
get hotter, it becomes more difficult for current to flow through them, which results in a
general slowdown of the system. Over time, this will also degrade the components and
cause them to fail.
High heat or prolonged heat produces the second effect, which is damage to components.
Capacitors and chips can both be damaged by heat, causing them to physically
rupture/break and stop working. This kind of failure generally results in the machine
stopping and no longer working until the damaged components are replaced, which is
often surprisingly expensive.
Heat is often much worse in laptops than in desktops, because laptops have smaller cases
with smaller fans and reduced air circulation. Be extra careful about making sure that
laptop fans are not blocked, and it can be a good idea to get a cooling mat for the laptop
to help it get rid of excess heat.
The main thing to do to keep your computer from overheating is to ensure that the fans
are not blocked or slowed by anything. Fans can easily be blocked by piling items around
your computer, by forcing the computer against a wall or desk, or by foreign objects
falling into the casing. Fans can be slowed by many of the above issues, but can also be
slowed by buildup of foreign matter on the fan blades. This is most often seen in
computers that are used by heavy smokers, but can also be produced by air freshener
spray and other airborne particulates. In general, this may not be an issue, but if there is a
great deal of pollution in the environment, the fans should be checked to make sure that
they can function properly.
Liquids. Liquids can damage a computer in two ways: by water damage to components
or by causing short circuits. Water damage to components is rare, and generally only
occurs in extremely high humidity or flood conditions. In these cases, mold can grow on
components, causing them to degrade (some molds are capable of digesting plastics and
soft metals) or moisture can soak the circuit boards, causing them to swell until the
electrical connections on the boards break. Generally it is not repairable, although it is
fairly uncommon.
Far more common is damage caused by liquid entering the case, which causes short
circuits. A short circuit is produced when the electricity in the machine finds an alternate
path to ground, and can seriously damage components by an increase in current. (For
more detail, see Appendix A: Basic Electrical Theory.)
Impact. Impact causes direct physical damage to the machine, ranging from cosmetic
(chipped or cracked bezels, scuffs) to the jarring loose of components such as cards, to
complete destruction of components. Impact should be avoided whenever possible. USB
devices are often quite vulnerable to this, as they often stick out in a way that exposes
them to being broken off; USB connectors are also easy to crush.
Basic Computer Knowledge Page 20
Component Failure. Components can fail for other reasons as well, including
mechanical wear on those items that have moving parts. This is most commonly seen in
fans, hard drives, and optical drives, which simply stop functioning; in general, the only
option at this point is to replace them. This is fairly cheap in the case of fans and optical
drives, much more expensive for hard drives, particularly if data recovery is required.
This is an excellent reason to ensure that good backups are being made. Computer
components, even those without moving parts, do not last forever, and there is always the
possibility that a piece will fail at any time.
Diagnosing component failures. Depending on the component that failed, this may
be very easy, or extremely difficult. A hard drive failure will generally exhibit the
following behavior:
1) Power button pressed
2) BIOS info/Manufacturer’s logo displays
3) Freeze or error message such as “Error reading Drive C”, “Missing operating
system” or “Primary Hard Disk Failure”.
If your system has this behavior, contact your tech support immediately! Hard drive
failure can be caused by an issue with the read/write head causing physical damage to the
drive platters, and if that is happening, then every time the drive is turned on, more data is
destroyed.
Determining which component has failed is done by:
1) Observing the system to see where it stops working. (In the example above, we
saw that the system failed at the point where boot control is handed over from
the BIOS, which is contained in a chip on the motherboard, to the OS, which
lives on the hard drive. This leads us to suspect either hard drive failure or a
corrupted OS – which may be a symptom of impending hard drive failure.)
2) Carefully noting error messages. If the error message we received above said
“Windows could not start because the following file is missing or corrupt…”,
we would think more about needing to repair Windows rather than having to
replace the drive.
3) When possible, testing components. If the system appears to start (lights come
on, fan is going, etc.) but no video is displayed, we should try switching out the
monitor – and test the original monitor on another system to see if it works
there. Figuring out if the problem follows the component or the machine is
critical to figuring out what goes on.
Software Damage.
Software damage to a computer can be caused by several things, including poorly written
updates, conflicts between applications, and malicious software.
Basic Computer Knowledge Page 21
Poorly written updates. It’s important to keep a system updated, but what if the
update is badly written? This can cause enormous issues, ranging from a system that
exhibits odd behavior, to complete system crashes. A badly written OS update might
even make the system unbootable. Generally, these are fixable by removing the update,
which is usually easy in the case of an application update1, or quite complicated in the
case of an OS update – these often require booting up in Safe Mode and using a restore
point to revert the update. If the system error is severe enough, it may be necessary to re-
install the OS. The only good thing about update issues is that they (usually) don’t result
in data loss, because it’s almost always possible to remove the drive and recover data
from it without the OS. The best defense against poorly written updates is to test updates
on a different machine first; failing that, make sure you have good backups and know
where your restore media is.
Application Conflicts. The modern computer system is a very complex environment;
between the OS and the applications, millions of lines of computer code are executed
every day. Sometimes code conflicts with other code, and then strange behavior can
occur, ranging from slowness to crashing and inability to boot. One case I ran into
involved a machine that was very slow on the internet, because the user had installed both
the Google and Yahoo toolbars, (probably at different times), had set each to be the
default search engine, and had told each to prevent changes to the search engine. Every
time the browser opened, the Google toolbar would change the search to Google, the
Yahoo toolbar would change it to Yahoo, and so on – the browser was slow because it
was spending almost all its time fighting about what search engine to use. Most examples
aren’t this easy to find, however; usually what you’ll see is an application crashing,
freezing or slowing down if another application is open or running. If it’s an application
that runs in the background, this can be particularly difficult to track down, because it
won’t be obvious why the crashes are occurring.
Troubleshooting steps. The first rule of troubleshooting is to isolate the problem and
begin to isolate its causes. Break the issue down as much as possible; if pressing the
power button doesn’t make the computer come on, what is it that doesn’t start? Is there
no response at all to the power button, or does the system begin to start and then stop?
Does it appear to start, but no video is displayed? If video is displayed, does it suddenly
stop?
Always start with the basics. If there is no response at all to the power button, make sure
the machine is plugged in. Check the power strip and outlet to make sure that they are
functioning; are other devices plugged into this receiving power? See if you can localize
the problem to the system, the power cable, to the outlet. Does the power button feel odd
when pressed? Power buttons sometimes break. Check it for physical failure.
1 Although some app updates can make the system unbootable – AVG had one of these in December 2010.
Basic Computer Knowledge Page 22
Appendix I - Basic electrical theory.
There are three main things we need to be aware of when dealing with electric devices:
the power used, the current required, and the voltage required. All of these are related,
and changing any one of them affects the others. We’ll also consider resistance, although
not as much – it mainly comes into play in short circuits.
v= voltage, measured in volts (V)
i= current, measured in amperes (amps) (A)
P=power, measured in watts (W)
r= resistance, measured in ohms (Ω)
Voltage can be thought of as the “push” of electrical current; it’s what drives the
electricity through the wires. Current is the “pool” of energy that the device draws on.
Power is a quick and easy way of relating the two, and of comparing devices; it’s easy to
see that a 1500W microwave uses more power per minute than a 450W computer does.
Power is related to voltage and current through the following equation:
P=vi (power is equal to voltage times current)
Computer power supplies are rated in terms of watts, such as 450W or 550W. From the
equation, we can see that a 450W power supply, plugged into 115 volts from the wall, is
capable of supplying 3.91 amps. (450W=115V times 3.91 amps) Most of the time we
don’t need to know this sort of thing, but when replacing a power supply it comes in
handy.
Voltage and current are also related to resistance through the following equation:
v=ir (voltage is equal to the current times the resistance),
which is often written as
i=v/r (current is equal to voltage divided by the resistance)
This is mainly going to be important if there’s a short circuit. When a short develops,
current no longer flows through the entire circuit. Instead, it finds a shorter path and
travels through only part of the circuit. The shorter path ALWAYS has less resistance;
since the resistance drops, the current goes up, often very quickly.
Example: Let’s imagine a 12V circuit that comes out of the power supply, passes through
the hard drive (powering its motor) and through a DVD drive (likewise powering it). For
our purposes (assuming a 6 ohm resistance), the equation above shows that the current
(amps) used by the circuit is:
i=12/6 = 2 amps
Basic Computer Knowledge Page 23
– that is, the circuit normally will draw 2 amps of current. One day, the computer user
spills a drink into the machine, causing a short. The resistance is abruptly cut to 1/10th
its
normal level. Now we have:
i=12/0.6 = 20 amps
That level of current has a good chance of burning out some of the components on the
circuit.
Basic Computer Knowledge Page 24
Appendix II – Computer Ports Quick Reference
USB Types
(Duye, 2009)
PS/2 keyboard/mouse
(Rogers, 2004)
VGA Video
(Lithgow, 2006) DVI Video
(Mobius, 2006)
Basic Computer Knowledge Page 25
HDMI Video
(Bautsch, 2006)
DisplayPort
(Abisys, 2008)
S-Video
(Gh5046, 2008)
Network jack
Basic Computer Knowledge Page 26
Serial port
(Lithgow, 2006)
Parallel port
(Lithgow, 2006)
Firewire/IEEE1394
(KoS, 2006)
Audio out/speaker/ Audio in/microphone
Basic Computer Knowledge Page 27
Appendix III – Further reading
Electrical Theory
The ARRL Ham Radio License Manual – American Radio Relay League, 2006
Electronics for Dummies – Shamieh and Macomb, 2009
Teach Yourself Electricity and Electronics, 5th Edition – Gibilisco, 2011
Computer Theory
PCs for Dummies – Gookin, 2007
PCs for Dummies, Windows 7 Edition – Gookin, 2009
Absolute Beginner’s Guide to Computer Basics – Miller, 2009
Easy Computer Basics, Windows 7 Edition – Miller, 2009
Computer Repair with Diagnostic Flowcharts: Troubleshooting PC Hardware Problems
from Boot Failure to Poor Performance, Revised Edition – Rosenthal, 2011
Basic Computer Knowledge Page 28
Appendix IV – Quiz
1.) What are the two main parts of a computer system? How are they related?
2.) What is the motherboard?
3.) Why do hard drives and fans wear out?
4.) What is the CPU?
5.) How do RAM, bus speed, and CPU speed all contribute to how fast a computer
is?
6.) How does more RAM speed up a computer?
7.) Describe three types of video connectors. How are they different? Which is best?
8.) Why is liquid dangerous for computers?
9.) What makes a computer overheat?
Basic Computer Knowledge Page 29
Works Cited Abisys. (2008, July 20). File:DisplayPort Connector.svg. Retrieved November 30, 2011,
from Wikipedia: http://en.wikipedia.org/wiki/File:DisplayPort_Connector.svg
Bautsch. (2006, July 06). File:HDMI.socket.png. Retrieved November 30, 2011, from
Wikipedia: http://en.wikipedia.org/wiki/File:HDMI.socket.png
Duye, B. (2009, January 1). File:Types-usb new.svg. Retrieved September 16, 2011, from
Wikipedia: http://en.wikipedia.org/wiki/File:Types-usb_new.svg
Gh5046. (2008, March 21). File:S-Video 7-pin quasi-DIN connector.JPG. Retrieved 11
17, 2011, from Wikimedia Commons: http://commons.wikimedia.org/wiki/File:S-
Video_7-pin_quasi-DIN_connector.JPG
Gustavb. (2006). File:Personal computer, exploded.svg. Retrieved January 13, 2012,
from Wikimedia Commons:
http://commons.wikimedia.org/wiki/File:Personal_computer,_exploded.svg
KoS. (2006, August 29). File:Firewire.jpg. Retrieved January 13, 2012, from Wikimedia
Commons: http://commons.wikimedia.org/wiki/File:Firewire.jpg
Lithgow, D. (2006, May 24). File:Parallel computer printer port.jpg. Retrieved January
13, 2012, from Wikimedia Commons:
http://commons.wikimedia.org/wiki/File:Parallel_computer_printer_port.jpg
Lithgow, D. (2006, May 24). File:Serial port.jpg. Retrieved 1 13, 2012, from Wikimedia
Commons: http://commons.wikimedia.org/wiki/File:Serial_port.jpg
Lithgow, D. (2006, May 24). File:SVGA port.jpg. Retrieved November 30, 2011, from
Wikipedia: http://en.wikipedia.org/wiki/File:SVGA_port.jpg
Mobius. (2006, May 15). File:DVI Connector Types.svg. Retrieved November 30, 2011,
from Wikipedia: http://en.wikipedia.org/wiki/File:DVI_Connector_Types.svg
Rogers, N. (2004, October 16). File:Ps-2-ports.jpg. Retrieved November 30, 2011, from
Wikipedia: http://en.wikipedia.org/wiki/File:Ps-2-ports.jpg