10+2 Date Entry Ans

8/12/2019 10+2 Date Entry Ans

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Question Paper March 2014

Degree Bridge Course (Equivalent to 102 !td"#$

!u%& Data Entr' (DBC D$)i*e+ hours Ma,i*u* +-0

." /nser the olloing question in one sentence each& 10 , 110

1. Expand CPU. central processing unit2. What is Ram? RANDOM ACCESS MEMORY3. What is the functin f MAR? MARholds the memory location of data that needs to be

accessed. When reading from memory,!. Name an" ne f the US# De$ise. SCAN%E&5. Expand SDRM. Synchronous dynamic random memory6. What is W'm? malwarecomputer program7. Expand SDRM. Synchronous dynamic random memory

8. Expand US#. Universal Serial Bus(USB)

9. What is cmpute' c(c) speed? , 1.50 GHz 1.! GHz*+. Exp(ain inst'uctin set.

.." /nser an' ten o the olloing question in 2 to sentences each& 10 , 2 20

**. W'ite at (east , t - cmpnents f the Mthe' #a'd.

*2. W'ite the Name f the fi$e sus"stems t cnt'( the net/').

i0 S&ORA1E MODUES ii0 3UNC&4ONAMODUES 5pe'at's0 iii0DA&APA&6S 5s/itches and /i'es0i$0 CON&RO PO4N&S $0 COND4&4ON PO4N&S

*7. What is PC ca'd?

A PC Card (previously known as a PCMCIA card is a credi! card"si#e $e$oryorI%&device !'a! i!sin!o a personal co$pu!er) usually a no!e*ook or lap!op co$pu!er. Pro*a*ly !'e $os! co$$on use oa PC Card is !'e !eleco$$unica!ions $ode$or no!e*ook co$pu!ers. +'ere are 16"*inary di,i!and3-"*i! (Cardus varie!ies o PC Cards. Ano!'er !ype o PC card is !'e/0 por!Card.

*!. 6/ 8ice Mai( W')s.

" call to any business or home used to mean one of three things ## an answer, a busy signal or

endless, unanswered ringing. $ncreasingly, it now means an encounter with %oice mail. %oice

messages ha%e become a routine part of e%eryone&s day, if not the most common electronic message

system used. "t wor', on your cell phone and at home, almost e%eryone has at least one %oice mail

account, and sometimes more than one.

*,. 3e/ D'a/ac)s f E(ect'nic Mai(.

The recipient needs access to the Internet to receive email.

Virusesare easily spread via email attachments(most email providers scan emails for

viruses on your behalf).

Phishing- sending an email to a user falsely claiming to be a legitimate company to

scam the user into providing information, such as personal information and bankaccount numbers on a bogus website. The details will then be used for identity theft.
http://en.wikipedia.org/wiki/Central_processing_unithttp://en.wikipedia.org/wiki/Malwarehttp://en.wikipedia.org/wiki/Computer_programhttp://searchmobilecomputing.techtarget.com/definition/memoryhttp://searchmobilecomputing.techtarget.com/definition/memoryhttp://searchcio-midmarket.techtarget.com/definition/input-outputhttp://searchcio-midmarket.techtarget.com/definition/input-outputhttp://searchmobilecomputing.techtarget.com/definition/modemhttp://searchcio-midmarket.techtarget.com/definition/bithttp://whatis.techtarget.com/definition/ZV-port-Zoomed-Video-porthttp://en.wikipedia.org/wiki/Central_processing_unithttp://en.wikipedia.org/wiki/Malwarehttp://en.wikipedia.org/wiki/Computer_programhttp://searchmobilecomputing.techtarget.com/definition/memoryhttp://searchcio-midmarket.techtarget.com/definition/input-outputhttp://searchmobilecomputing.techtarget.com/definition/modemhttp://searchcio-midmarket.techtarget.com/definition/bithttp://whatis.techtarget.com/definition/ZV-port-Zoomed-Video-port


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No guarantee the mail will be read until the user logs on and checks their email.

Spam- unsolicited email, ie unk mail.

*-. 3u(( Dup(ex." duplexcommunication systemis a point#to#pointsystem composed of two connected parties orde%ices that can communicate with one another in both directions, simultaneously. "n eample ofa duple de%ice is a telephone. )he people at both ends of a telephone call can spea' at thesame time and simultaneously each be heard by the other at the same time. )he earphone

reproduces the speech of the other person as the microphone transmits the speech of the localperson, because there is a two#way communication channel between them.*9. Exp(ain Se'ia( Data &'ansmissin.

$n telecommunicationand computer science, serial communicationis the process of

sending dataone bitat a time, se*uentially, o%er acommunication channelor computer bus. )his is in

contrast to parallel communication, where se%eral bits are sent as a whole, on a lin' with se%eral

parallel channels.

+erial communication is used for all long#haul communication and most computer networ's, where

the cost of cableand synchronizationdifficulties ma'e parallel communication impractical. +erial

computer buses are becoming more common e%en at shorter distances, as impro%ed signal

integrityand transmission speeds in newer serial technologies ha%e begun to outweigh the parallelbus&s ad%antage of simplicity (no need for serializer and deserializer, or +eres- and to outstrip its

disad%antages (cloc' s'ew, interconnect density-. )he migration from /$to/$ pressis an

eample.

*:. E(a'ate n Data Definitin (an;ua;e.

ata efinition anguage is used to modify the schema of the database. $t will ne%er impact the userrights for the database. 2therwise, it can erase records in some tables. $t describes three statements3/4"), ")4 and 42.

*


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point ftp.example.comand www.example.comto the" recordexample.com, which in turn points to the $#

address. )hen, if you e%er need to change the $#address, you only ha%e to change it in one place (" record-.

/": records must always be pointed to another domain name, ne%er to an $#address.

2*. What is the cmmn use f (in)in; data?

Common Data Lin !CDL)is a secure ;.+. militarycommunications protocol. $t was established by

the ;.+. epartment of efensein 1/ operates within the @ubandat data rates up to ?AB :bits. / allows forfulldupledata echange.

)he 790C "uthorization "ct (ublic aw 10


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2ther such cables and ports, transmitting data one bit at a time, include +erial ")", +erial

+/+$, thernet cableplugged into thernet ports, theisplay ata /hannelusing pre%iously reser%ed

pins of the FG" connectoror the F$ portor the H:$port.

Serial #uses

:any communication systems were generally originally designed to connect two integrated circuits on

the same printed circuit board,connected bysignal traceson that board (rather than eternal cables-.

$ntegrated circuitsare more epensi%e when they ha%e more pins. )o reduce the number of pins in apac'age, many $/s use a serial bus to transfer data when speed is not important. +ome eamples of

such low#cost serial buses include +$, $/, ;$2, and 1#Wire.

Serial versus parallel

)he communication lin's across which computersor parts of computerstal' to one another may

be either serial or parallel. " parallel lin' transmits se%eral streams of data simultaneously along

multiple channels (e.g., wires, printed circuit trac's, or optical fibres-8 a serial lin' transmits a single

stream of data.

"lthough a serial lin' may seem inferior to a parallel one, since it can transmit less data per cloc'

cycle, it is often the case that serial lin's can be cloc'ed considerably faster than parallel lin's inorder to achie%e a higher data rate. " number of factors allow serial to be cloc'ed at a higher rate3

/loc' s'ewbetween different channels is not an issue (for uncloc'ed asynchronous serial

communicationlin's-.

" serial connection re*uires fewer interconnecting cables (e.g., wiresfibres- and hence

occupies less space. )he etra space allows for better isolation of the channel from its

surroundings.

/rosstal'is less of an issue, because there are fewer conductors in proimity.

$n many cases, serial is a better option because it is cheaper to implement. :any $/sha%e serialinterfaces, as opposed to parallel ones, so that they ha%e fewer pins and are therefore less

epensi%e.

2!. Exp(ain Pa'a((e( Data &'ansmissin.

$n telecommunicationand computer science, parallel communicationis a method of con%eying

multiple binary digits (bits- simultaneously. $t contrasts with serial communication, which con%eys only

a single bit at a time8 this distinction is one way of characterizing a communications lin'.

)he basic difference between a parallel and a serial communication channelis the number of

electrical conductors used at the physical layerto con%ey bits. arallel communication implies more

than one such conductor. 7or eample, an I#bit parallel channel will con%ey eight bits (or a byte-

simultaneously, whereas a serial channel would con%ey those same bits se*uentially, one at a time. $f

both channels operated at the same cloc' speed, the parallel channel would be eight times faster. "

parallel channel may ha%e additional conductors for other signals, such as a cloc' signal to pace the

flow of data, a signal to control the direction of data flow, and handsha'ingsignals.

Defore the de%elopment of high#speed serial technologies, the choice of parallel lin's o%er serial lin's

was dri%en by these factors3
http://en.wikipedia.org/wiki/Serial_ATAhttp://en.wikipedia.org/wiki/SCSI_connector#Serial_SCSIhttp://en.wikipedia.org/wiki/SCSI_connector#Serial_SCSIhttp://en.wikipedia.org/wiki/Ethernet_cablehttp://en.wikipedia.org/wiki/Ethernet_porthttp://en.wikipedia.org/wiki/Display_Data_Channelhttp://en.wikipedia.org/wiki/VGA_connectorhttp://en.wikipedia.org/wiki/VGA_connectorhttp://en.wikipedia.org/wiki/DVI_porthttp://en.wikipedia.org/wiki/HDMIhttp://en.wikipedia.org/wiki/Printed_circuit_boardhttp://en.wikipedia.org/wiki/Printed_circuit_boardhttp://en.wikipedia.org/wiki/Signal_tracehttp://en.wikipedia.org/wiki/Integrated_circuithttp://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bushttp://en.wikipedia.org/wiki/I%C2%B2Chttp://en.wikipedia.org/wiki/UNI/Ohttp://en.wikipedia.org/wiki/1-Wirehttp://en.wikipedia.org/wiki/Clock_skewhttp://en.wikipedia.org/wiki/Asynchronous_serial_communicationhttp://en.wikipedia.org/wiki/Asynchronous_serial_communicationhttp://en.wikipedia.org/wiki/Crosstalkhttp://en.wikipedia.org/wiki/Integrated_circuithttp://en.wikipedia.org/wiki/Telecommunicationhttp://en.wikipedia.org/wiki/Computer_sciencehttp://en.wikipedia.org/wiki/Bithttp://en.wikipedia.org/wiki/Serial_communicationhttp://en.wikipedia.org/wiki/Communication_channelhttp://en.wikipedia.org/wiki/Physical_layerhttp://en.wikipedia.org/wiki/Physical_layerhttp://en.wikipedia.org/wiki/Bytehttp://en.wikipedia.org/wiki/Clock_speedhttp://en.wikipedia.org/wiki/Handshakinghttp://en.wikipedia.org/wiki/Serial_ATAhttp://en.wikipedia.org/wiki/SCSI_connector#Serial_SCSIhttp://en.wikipedia.org/wiki/SCSI_connector#Serial_SCSIhttp://en.wikipedia.org/wiki/Ethernet_cablehttp://en.wikipedia.org/wiki/Ethernet_porthttp://en.wikipedia.org/wiki/Display_Data_Channelhttp://en.wikipedia.org/wiki/VGA_connectorhttp://en.wikipedia.org/wiki/DVI_porthttp://en.wikipedia.org/wiki/HDMIhttp://en.wikipedia.org/wiki/Printed_circuit_boardhttp://en.wikipedia.org/wiki/Signal_tracehttp://en.wikipedia.org/wiki/Integrated_circuithttp://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bushttp://en.wikipedia.org/wiki/I%C2%B2Chttp://en.wikipedia.org/wiki/UNI/Ohttp://en.wikipedia.org/wiki/1-Wirehttp://en.wikipedia.org/wiki/Clock_skewhttp://en.wikipedia.org/wiki/Asynchronous_serial_communicationhttp://en.wikipedia.org/wiki/Asynchronous_serial_communicationhttp://en.wikipedia.org/wiki/Crosstalkhttp://en.wikipedia.org/wiki/Integrated_circuithttp://en.wikipedia.org/wiki/Telecommunicationhttp://en.wikipedia.org/wiki/Computer_sciencehttp://en.wikipedia.org/wiki/Bithttp://en.wikipedia.org/wiki/Serial_communicationhttp://en.wikipedia.org/wiki/Communication_channelhttp://en.wikipedia.org/wiki/Physical_layerhttp://en.wikipedia.org/wiki/Bytehttp://en.wikipedia.org/wiki/Clock_speedhttp://en.wikipedia.org/wiki/Handshaking


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+peed3 +uperficially, the speed of a parallel data lin' is e*ual to the number of bits sent at one

time times the bit rateof each indi%idual path8 doubling the number of bits sent at once doubles

the data rate. $n practice, cloc' s'ewreduces the speed of e%ery lin' to the slowest of all of the

lin's.

/able length3 /rosstal'creates interference between the parallel lines, and the effect worsens

with the length of the communication lin'. )his places an upper limit on the length of a parallel

data connection that is usually shorter than a serial connection.

/ompleity3 arallel data lin's are easily implemented in hardware, ma'ing them a logicalchoice. /reating a parallel portin a computer system is relati%ely simple, re*uiring only a latchto

copy data onto a data bus. $n contrast, most serial communication must first be con%erted bac'

into parallel form by a uni%ersal asynchronous recei%ertransmitter(;"4)- before they may be

directly connected to a data bus.

)he decreasing cost of integrated circuits, combined with greater consumer demand for speed and

cable length, has led to parallel communication lin's becoming deprecated in fa%or of serial lin's8 for

eample, $ 1?IBprinter ports %s. ;+D, arallel ")"%s. +erial ")", and +/+$%s. 7ireWire.

2n the other hand, there has been a resurgence of parallel data lin's in 47communication. 4ather

than transmitting one bit at a time (as in :orse codeand D+@-, well#'nown techni*ues suchas +:, ":, and :ultiple#input multiple#outputcommunication send a few bits in parallel. (ach

such group of bits is called a 6symbol6-. +uch techni*ues can be etended to send an entire byte at

once (?5C#J":-. :ore recently techni*ues such as 27:ha%e been used in"symmetric igital

+ubscriber ineto transmit o%er ??B bits in parallel, and in FD#)to transmit o%er C0BI bits in

parallel.

2,. 8a'ius ad$anta;es f usin; D#MS.

)here are many ways to store your data, so what are the ad%antages of using a atabase

:anagement +ystem (D:+- li'e +par'leD o%er other storage typesK

ata independence

Application programs should be as independent as possible from details of data representation and storage. The

DBMS can provide an abstract view of the data to insulate application code from such details.

fficient data access

A DBMS utilizes a variety of sophisticated techniques to store and retrieve data efficiently. This feature is

especially important if the data is stored on eternal storage devices.

ata integrity and security

!f data is always accessed through the DBMS" the DBMS can enforce integrity constraints on the data. #or

eample" before inserting salary information for an employee" the DBMS can chec$ that the department budget
http://en.wikipedia.org/wiki/Bit_ratehttp://en.wikipedia.org/wiki/Clock_skewhttp://en.wikipedia.org/wiki/Crosstalk_(electronics)http://en.wikipedia.org/wiki/Parallel_porthttp://en.wikipedia.org/wiki/Latch_(electronic)http://en.wikipedia.org/wiki/Data_bushttp://en.wikipedia.org/wiki/Universal_asynchronous_receiver/transmitterhttp://en.wikipedia.org/wiki/Integrated_circuitshttp://en.wikipedia.org/wiki/IEEE_1284http://en.wikipedia.org/wiki/USBhttp://en.wikipedia.org/wiki/Parallel_ATAhttp://en.wikipedia.org/wiki/Serial_ATAhttp://en.wikipedia.org/wiki/SCSIhttp://en.wikipedia.org/wiki/FireWirehttp://en.wikipedia.org/wiki/Radio_frequencyhttp://en.wikipedia.org/wiki/Morse_codehttp://en.wikipedia.org/wiki/Morse_codehttp://en.wikipedia.org/wiki/BPSKhttp://en.wikipedia.org/wiki/Phase-shift_keyinghttp://en.wikipedia.org/wiki/Pulse-amplitude_modulationhttp://en.wikipedia.org/wiki/Multiple-input_multiple-outputhttp://en.wikipedia.org/wiki/Symbol_(data)http://en.wikipedia.org/wiki/256-QAMhttp://en.wikipedia.org/wiki/OFDMhttp://en.wikipedia.org/wiki/Asymmetric_Digital_Subscriber_Linehttp://en.wikipedia.org/wiki/Asymmetric_Digital_Subscriber_Linehttp://en.wikipedia.org/wiki/DVB-Thttp://en.wikipedia.org/wiki/Bit_ratehttp://en.wikipedia.org/wiki/Clock_skewhttp://en.wikipedia.org/wiki/Crosstalk_(electronics)http://en.wikipedia.org/wiki/Parallel_porthttp://en.wikipedia.org/wiki/Latch_(electronic)http://en.wikipedia.org/wiki/Data_bushttp://en.wikipedia.org/wiki/Universal_asynchronous_receiver/transmitterhttp://en.wikipedia.org/wiki/Integrated_circuitshttp://en.wikipedia.org/wiki/IEEE_1284http://en.wikipedia.org/wiki/USBhttp://en.wikipedia.org/wiki/Parallel_ATAhttp://en.wikipedia.org/wiki/Serial_ATAhttp://en.wikipedia.org/wiki/SCSIhttp://en.wikipedia.org/wiki/FireWirehttp://en.wikipedia.org/wiki/Radio_frequencyhttp://en.wikipedia.org/wiki/Morse_codehttp://en.wikipedia.org/wiki/BPSKhttp://en.wikipedia.org/wiki/Phase-shift_keyinghttp://en.wikipedia.org/wiki/Pulse-amplitude_modulationhttp://en.wikipedia.org/wiki/Multiple-input_multiple-outputhttp://en.wikipedia.org/wiki/Symbol_(data)http://en.wikipedia.org/wiki/256-QAMhttp://en.wikipedia.org/wiki/OFDMhttp://en.wikipedia.org/wiki/Asymmetric_Digital_Subscriber_Linehttp://en.wikipedia.org/wiki/Asymmetric_Digital_Subscriber_Linehttp://en.wikipedia.org/wiki/DVB-T


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is not eceeded. Also" the DBMS can enforce access controls that govern what data is visible to different classes

of users.

ata administration

%hen several users share the data" centralizing the administration of data can offer significant improvements.

&perienced professionals who understand the nature of the data being managed" and how different groups of

users use it" can be responsible for organizing the data representation to minimize redundancy and for retuning

the storage of the data to ma$e retrieval efficient.

/oncurrent access and crash reco%ery

A DBMS schedules concurrent accesses to the data in such a manner that users can thin$ of the data as being

accessed by only one user at a time. #urther" the DBMS protects users from the effects of system failures.

4educed application de%elopment time

'learly" the DBMS supports many important functions that are common to many applications accessing data

stored in the DBMS. This" in con(unction with the high)level interface to the data" facilitates quic$ development

of applications. Such applications are also li$ely to be more robust than applications developed from scratch

because many important tas$s are handled by the DBMS instead of being implemented by the application.

2-. Exp(ain E(ect'nics Data P'cessin;.Electronic Data $rocessin%(ED$- can refer to the use of automated methods to processcommercial data. )ypically, this uses relati%ely simple, repetiti%e acti%ities to process large %olumes ofsimilar information. 7or eample3 stoc' updates applied to an in%entory, ban'ing transactions appliedto account and customer master files, boo'ing and tic'eting transactions to an airline&s reser%ationsystem, billing for utility ser%ices. )he modifier 6electronic6 or 6automatic6 was used with 6dataprocessing6 (-, especially ca. 1. arly commercial systems were installed eclusi%ely by large organizations. )hese could afford to

in%est the time and capital necessary to purchase hardware, hire specialist staff to de%elop

bespo'e softwareand wor' through the conse*uent (and often unepected- organizational and

cultural changes.

"t first, indi%idual organizations de%eloped their own software, including data management utilities,

themsel%es. ifferent products might also ha%e &one#off& bespo'e software. )his fragmented approach
http://en.wikipedia.org/wiki/Data_processinghttp://en.wikipedia.org/wiki/Data_processinghttp://en.wikipedia.org/wiki/United_Kingdomhttp://en.wikipedia.org/wiki/J._Lyons_and_Co.http://en.wikipedia.org/wiki/J._Lyons_and_Co.http://en.wikipedia.org/wiki/Electronic_data_processing#cite_note-3http://en.wikipedia.org/wiki/LEO_computerhttp://en.wikipedia.org/wiki/LEO_computerhttp://en.wikipedia.org/wiki/LEO_computerhttp://en.wikipedia.org/wiki/Electronic_data_processing#cite_note-4http://en.wikipedia.org/wiki/Softwarehttp://en.wikipedia.org/wiki/Data_processinghttp://en.wikipedia.org/wiki/Data_processinghttp://en.wikipedia.org/wiki/United_Kingdomhttp://en.wikipedia.org/wiki/J._Lyons_and_Co.http://en.wikipedia.org/wiki/J._Lyons_and_Co.http://en.wikipedia.org/wiki/Electronic_data_processing#cite_note-3http://en.wikipedia.org/wiki/LEO_computerhttp://en.wikipedia.org/wiki/Electronic_data_processing#cite_note-4http://en.wikipedia.org/wiki/Software


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led to duplicated effort and the production of management information needed manual effort. =citation

needed>

High hardware costs and relati%ely slow processing speeds forced de%elopers to use resources

&efficiently&. ata storageformats were hea%ily compacted, for eample. " common eample is the

remo%al of the century from dates, which e%entually led to the &millennium bug&.

ata input re*uired intermediate processing %ia punched paper tape or punched cardand separate

input to a repetiti%e, labor intensi%e tas', remo%ed from user control and error#prone. $n%alid or

incorrect data needed correction and resubmission with conse*uences for data and accountreconciliation.

29. Wh" C (an;ua;e is is ppu(a'.2:. Exp(ain #asic input and utput functins.

." /nser an' to o the olloing question in 0 to 40 sentences each& 2 , 1020

2


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Figure 1. The Systems Failure Analysis Process. This approach assures root causeidentification and effective corrective action implementation.

7igure 1 shows our recommended systems failure analysis approach. +ystems failure analysis beginswith a clear understanding of the failure (i.e., a definition of the problem-. 2nce this has beenaccomplished, all potential failure causes are identified using fault tree analysis. )he process thanobMecti%ely e%aluates each of the potential failure causes using se%eral techni*ues, including 6what&sdifferent6 analysis, pedigree analysis, failed hardware analysis, and designed eperiments. )hesetechni*ues help in con%erging on the causes of failure among many identified potential causes. 2nce

the failure causes ha%e been identified, the approach outlined herein de%elops a range of correcti%eactions and then selects and trac's optimum correcti%e action implementation.

&ault "ree Analysis' (dentiyin% All $otential &ailure Causes

When confronted with a systems failure, there is often a natural tendency to begin disassemblinghardware to search for the cause. )his is a poor approach. 7ailed hardware can re%eal %aluableinformation and safeguards are necessary to pre%ent losing that information from careless teardownprocedures. 2ne must 'now what to loo' for prior to disassembling failed hardware. )his is wherefault tree analysis enters the picture.

7ault tree analysis is a graphical techni*ue that identifies all potential failure causes. )he approachwas de%eloped in the early 1


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We&ll eamine a simple eample to see how this is done, but first, let&s consider fault tree analysissymbology. 7igure ? shows the symbols used by the fault tree. )here are two categories ofsymbols3 e%ents and gates. et&s first consider the four different symbols for e%ents. )he rectangle iscalled a command e%ent, and it represents a condition that is induced by the e%ents immediately belowit (we&ll see how shortly-. )he circle represents a basic failure e%ent (these are typically componentfailures, such as a resistor failing open, or a structural member crac'ing-. )he house represents anormally occurring e%ent (for eample, if electrical power is normally present on a power line, the housewould be used to represent this e%ent-. )he last e%ent symbol is the diamond (it loo's li'e a rectangle

with the corners remo%ed-, which can represent either a human error or an unde%eloped e%ent. "human error might be a pilot&s failure to etend the landing gear when landing an aircraft, a technician&sfailure to properly adMust a %ariable resistor, or a crew member inad%ertently depressing a self#destructbutton on a missile control console. "n unde%eloped e%ent is one that re*uires no furtherde%elopment. ;sually command e%ents considered etremely unli'ely are designated as unde%elopede%ents to show that they ha%e been considered and eliminated as a possible failure causes. 7ault treee%ents are lin'ed by gates to show the relationships between the e%ents. )here are two types ofgates3 6and6 gates, and 6or6 gates. )he 6and6 gate signifies that all e%ents beneath it must occursimultaneously to result in the e%ent abo%e it. )he 6or6 gate means that if any of the e%ents beneath itoccur, the e%ent abo%e it will result.

Figure 2. Fault Tree Symbology. Different symbols represent events and logic gates.

)he best approach for de%eloping the fault tree is to assemble a team consisting of personnel with agood understanding of how the system is supposed to operate and associated support functions. )heteam should typically include an engineer, a *uality engineer, a manufacturing engineer, an assemblytechnician, and perhaps others, depending on the nature of the failure.

et&s now eamine how all of the abo%e comes together to generate a fault tree analysis. We&llconsider a simple systems failure analysis. +uppose we ha%e a system with a light bulb that screwsinto a soc'et, and the light bulb illuminates when someone turns a switch on. 7igure ! shows aschematic for this system. 2ne day, we flip the switch and the light bulb does not come on.


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Figure 3. ight !ulb "iring Schematic. This is the system for #hich #e$ll prepare a fault treeanalysis.

)he first step to define the problem. )he problem here is that the light bulb does not illuminate. )hisbecomes the top undesired e%ent in the fault tree for this system failure, and 7igure B shows it in acommand e%ent (the rectangle symbol-. )op undesired e%ents are always shown in a command e%entsymbol, as they will be commanded to occur by e%ents in the tree below.

Figure %. &ndicator ight Fault Tree Analysis. This simple fault tree develops potential causesfor an indicator light system failing to illuminate.


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)he net step is to loo' for the immediately adMacent causes that can induce the top undesirede%ent. )his is a critically important concept. " common shortcoming is to Mump around in the system,and start listing things li'e a power loss in the building, a failed switch, and perhaps other e%ents, butthe fault tree re*uires discipline. 2ne has to loo' for the internal or immediately adMacent causes. "napproach for doing this is to imagine yourself as the light bulb, screwed into the soc'et, and as' 6whatcan happen in me or right net to me to pre%ent me from illuminatingK6 $f one considers only theseconditions, the answers are3

"n open light bulb filament /ontaminated terminals in the soc'et

" bulb that&s not fully screwed into the soc'et

o electrical energy from the soc'et

We show these e%ents immediately below the top undesired e%ent and determine which symbol isappropriate for each. )he open filament is a basic component failure, so it goes in a circlesymbol. /ontaminated terminals in the soc'et could be caused by a %ariety of conditions, but for thepurposes of this analysis we won&t fully de%elop these, and we&ll put contaminated terminals in an

unde%eloped e%ent symbol (the diamond-. ot fully screwing the bulb into the soc'et is a human error,so it goes into a human error symbol (also a diamond-. 7inally, no energy from the soc'et is acondition that will be commanded to occur if other e%ents occur elsewhere in the system. )his e%entbecomes a command e%ent, and it goes into a rectangle.

7+. Exp(ain aut Cmpute' Secu'it".

Computer security(also 'nown as cy#ersecurityor (" security- is information securityas applied

tocomputersand computer networ's.

)he field co%ers all the processes and mechanisms by which computer#based e*uipment, information

and ser%ices are protected from unintended or unauthorized access, change or destruction.

/omputer security also includes protection from unplanned e%ents and natural disasters.

+ecurity by design, or alternately secure by design, means that the software has been designed from

the ground up to be secure. $n this case, security is considered as a main feature.

+ome of the techni*ues in this approach include3

)he principle of least pri%ilege, where each part of the system has only the pri%ileges that are

needed for its function. )hat way e%en if an attac'ergains access to that part, they ha%e only

limited access to the whole system.

"utomated theorem pro%ing to pro%e the correctness of crucial software subsystems.

/ode re%iews and unit testingare approaches to ma'e modules more secure where formal

correctness proofs are not possible.

efense in depth, where the design is such that more than one subsystem needs to be

%iolated to compromise the integrity of the system and the information it holds.

efault secure settings, and design to 6fail secure6 rather than 6fail insecure6 (see fail#safefor

the e*ui%alent in safety engineering-. $deally, a secure system should re*uire a deliberate,
http://en.wikipedia.org/wiki/Information_securityhttp://en.wikipedia.org/wiki/Computerhttp://en.wikipedia.org/wiki/Computer_networkhttp://en.wikipedia.org/wiki/Computer_networkhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Secure_by_designhttp://en.wikipedia.org/wiki/Principle_of_least_privilegehttp://en.wikipedia.org/wiki/Hacker_(computer_security)http://en.wikipedia.org/wiki/Automated_theorem_provinghttp://en.wikipedia.org/wiki/Code_reviewhttp://en.wikipedia.org/wiki/Unit_testinghttp://en.wikipedia.org/wiki/Defense_in_depth_(computing)http://en.wikipedia.org/wiki/Fail-safehttp://en.wikipedia.org/wiki/Safety_engineeringhttp://en.wikipedia.org/wiki/Information_securityhttp://en.wikipedia.org/wiki/Computerhttp://en.wikipedia.org/wiki/Computer_networkhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Secure_by_designhttp://en.wikipedia.org/wiki/Principle_of_least_privilegehttp://en.wikipedia.org/wiki/Hacker_(computer_security)http://en.wikipedia.org/wiki/Automated_theorem_provinghttp://en.wikipedia.org/wiki/Code_reviewhttp://en.wikipedia.org/wiki/Unit_testinghttp://en.wikipedia.org/wiki/Defense_in_depth_(computing)http://en.wikipedia.org/wiki/Fail-safehttp://en.wikipedia.org/wiki/Safety_engineering


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conscious, 'nowledgeable and free decision on the part of legitimate authorities in order to ma'e

it insecure.

"udit trails trac'ing system acti%ity, so that when a security breach occurs, the mechanism and

etent of the breach can be determined. +toring audit trails remotely, where they can only be

appended to, can 'eep intruders from co%ering their trac's.

7ull disclosure to ensure that when bugs are found the 6window of %ulnerability6 is 'ept as

short as possible.

+ecurity "rchitecture can be defined as the design artifactsthat describe how the security controls(security countermeasures- are positioned, and how they relate to the o%erall informationtechnology architecture. )hese controls ser%e to maintain the system&s *ualityattributes3 confidentiality,

2ne use of the term 6computer security6 refers to technology that is used to implement

secure operating systems. :uch of this technology is based on science de%eloped in the 1


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+ecure operating systems designed to meet medium robustness le%els of security functionality and

assurance ha%e seen wider use within both go%ernment and commercial mar'ets. :edium robust

systems may pro%ide the same security functions as high assurance secure operating systems but do

so at a lower assurance le%el (such as /ommon /riteria le%els "B or "5-. ower le%els mean

we can be less certain that the security functions are implemented flawlessly, and therefore less

dependable. )hese systems are found in use on web ser%ers, guards, database ser%ers, and

management hosts and are used not only to protect the data stored on these systems but also to

pro%ide a high le%el of protection for networ' connections and routing ser%ices.

$f the operating en%ironment is not based on a secure operating system capable of maintaining a

domain for its own eecution, and capable of protecting application code from malicious sub%ersion,

and capable of protecting the system from sub%erted code, then high degrees of security are

understandably not possible. While such secure operating systems are possible and ha%e been

implemented, most commercial systems fall in a &low security& category because they rely on features

not supported by secure operating systems (li'e portability, and others-. $n low security operating

en%ironments, applications must be relied on to participate in their own protection. )here are &best

effort& secure coding practices that can be followed to ma'e an application more resistant to malicious

sub%ersion.

$n commercial en%ironments, the maMority of software sub%ersion %ulnerabilitiesresult from a few'nown 'inds of coding defects. /ommon software defects include buffer o%erflows, format string

%ulnerabilities, integer o%erflow, and codecommand inMection. )hese defects can be used to cause

the target system to eecute putati%e data. Howe%er, the 6data6 contain eecutable instructions,

allowing the attac'er to gain control of the processo
http://en.wikipedia.org/wiki/Vulnerability_(computing)http://en.wikipedia.org/wiki/Buffer_overflowshttp://en.wikipedia.org/wiki/Format_string_vulnerabilitieshttp://en.wikipedia.org/wiki/Format_string_vulnerabilitieshttp://en.wikipedia.org/wiki/Integer_overflowhttp://en.wikipedia.org/wiki/Code_injectionhttp://en.wikipedia.org/wiki/Vulnerability_(computing)http://en.wikipedia.org/wiki/Buffer_overflowshttp://en.wikipedia.org/wiki/Format_string_vulnerabilitieshttp://en.wikipedia.org/wiki/Format_string_vulnerabilitieshttp://en.wikipedia.org/wiki/Integer_overflowhttp://en.wikipedia.org/wiki/Code_injection

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