comprehensive computer safety training for oces employees

Comprehensive Computer Safety Training for OCES Employees Module 1 – Basic Computer Knowledge

Basic Computer Knowledge

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.


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


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


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.


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


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


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


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.


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.


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


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


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)


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


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


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


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.


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.


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.


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.


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.


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


– 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.


Appendix II – Computer Ports Quick Reference

USB Types

(Duye, 2009)

PS/2 keyboard/mouse

(Rogers, 2004)

VGA Video

(Lithgow, 2006) DVI Video

(Mobius, 2006)


HDMI Video

(Bautsch, 2006)

DisplayPort

(Abisys, 2008)

S-Video

(Gh5046, 2008)

Network jack


Serial port

(Lithgow, 2006)

Parallel port

(Lithgow, 2006)

Firewire/IEEE1394

(KoS, 2006)

Audio out/speaker/ Audio in/microphone


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


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?


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

comprehensive computer safety training for oces employees

Documents