this practice book contains computer science … computer science test practice book subject-matter...

Graduate Record Examinations®

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Graduate Record Examinations Board.

COMPUTERSCIENCE

TESTPRACTICE

BOOK

This practice bookcontains

� one actual full-length GREComputer Science Test

� test-taking strategies

Become familiar with

� test structure and content

� test instructions andanswering procedures

Compare your practicetest results with theperformance of thosewho took the test at aGRE administration.

Visit GRE Online at www.gre.org

Copyright © 2001 by Educational Testing Service. All rights reserved.EDUCATIONAL TESTING SERVICE, ETS, the ETS logos, GRADUATE RECORD EXAMINATIONS,

and GRE are registered trademarks of Educational Testing Service.

Note to Test Takers: Keep this practice book until you receive your score report.The book contains important information about content specifications and scoring.

3COMPUTER SCIENCE TESTPRACTICE BOOK

Table of ContentsPurpose of the GRE Subject Tests ........................ 3

Development of the Subject Tests ....................... 3

Content of the Computer Science Test ............... 4

Preparing for a Subject Test ................................. 5

Test-Taking Strategies .......................................... 6

What Your Scores Mean ...................................... 6

Practice GRE Computer Science Test ................. 9

Scoring Your Subject Test .................................. 49

Evaluating Your Performance ............................. 52

Answer Sheet ..................................................... 53

Purpose of the GRESubject TestsThe GRE Subject Tests are designed to help graduateschool admission committees and fellowship sponsorsassess the qualifications of applicants in specific fieldsof study. The tests also provide you with an assessmentof your own qualifications.

Scores on the tests are intended to indicateknowledge of the subject matter emphasized inmany undergraduate programs as preparation forgraduate study. Because past achievement is usuallya good indicator of future performance, the scoresare helpful in predicting success in graduate study.Because the tests are standardized, the test scorespermit comparison of students from differentinstitutions with different undergraduate programs.For some Subject Tests, subscores are provided inaddition to the total score; these subscores indicatethe strengths and weaknesses of your preparation,and they may help you plan future studies.

The GRE Board recommends that scores on theSubject Tests be considered in conjunction with otherrelevant information about applicants. Because numer-ous factors influence success in graduate school,reliance on a single measure to predict success is notadvisable. Other indicators of competence typicallyinclude undergraduate transcripts showing coursestaken and grades earned, letters of recommendation,the GRE Writing Assessment score, and GRE GeneralTest scores. For information about the appropriate useof GRE scores, write to GRE Program, EducationalTesting Service, Mail Stop 57-L, Princeton, NJ 08541,or visit our Web site at www.gre.org/codelst.html.

Development of theSubject TestsEach new edition of a Subject Test is developed by acommittee of examiners composed of professors in thesubject who are on undergraduate and graduate facul-ties in different types of institutions and in differentregions of the United States and Canada. In selectingmembers for each committee, the GRE Program seeksthe advice of the appropriate professional associationsin the subject.

The content and scope of each test are specified andreviewed periodically by the committee of examiners.Test questions are written by the committee and byother faculty who are also subject-matter specialistsand by subject-matter specialists at ETS. All questionsproposed for the test are reviewed by the committeeand revised as necessary. The accepted questions areassembled into a test in accordance with the contentspecifications developed by the committee to ensureadequate coverage of the various aspects of the fieldand, at the same time, to prevent overemphasis on anysingle topic. The entire test is then reviewed andapproved by the committee.

4 COMPUTER SCIENCE TESTPRACTICE BOOK

Subject-matter and measurement specialists on theETS staff assist the committee, providing informationand advice about methods of test construction andhelping to prepare the questions and assemble the test.In addition, each test question is reviewed to eliminatelanguage, symbols, or content considered potentiallyoffensive, inappropriate for major subgroups of the test-taking population, or likely to perpetuate any negativeattitude that may be conveyed to these subgroups. Thetest as a whole is also reviewed to ensure that the testquestions, where applicable, include an appropriatebalance of people in different groups and different roles.

Because of the diversity of undergraduate curricula,it is not possible for a single test to cover all thematerial you may have studied. The examiners, there-fore, select questions that test the basic knowledge andskills most important for successful graduate study inthe particular field. The committee keeps the testup-to-date by regularly developing new editions andrevising existing editions. In this way, the test contentchanges steadily but gradually, much like most cur-ricula. In addition, curriculum surveys are conductedperiodically to ensure that the content of a testreflects what is currently being taught in the under-graduate curriculum.

After a new edition of a Subject Test is first admin-istered, examinees’ responses to each test question areanalyzed in a variety of ways to determine whethereach question functioned as expected. These analysesmay reveal that a question is ambiguous, requiresknowledge beyond the scope of the test, or is inappro-priate for the total group or a particular subgroup ofexaminees taking the test. Answers to such questionsare not used in computing scores.

Following this analysis, the new test edition isequated to an existing test edition. In the equatingprocess, statistical methods are used to assess thedifficulty of the new test. Then scores are adjusted sothat examinees who took a difficult edition of the testare not penalized, and examinees who took an easieredition of the test do not have an advantage. Varia-tions in the number of questions in the differenteditions of the test are also taken into account inthis process.

Scores on the Subject Tests are reported as three-digit scaled scores with the third digit always zero.The maximum possible range for all Subject Test totalscores is from 200 to 990. The actual range of scores fora particular Subject Test, however, may be smaller. Themaximum possible range of Subject Test subscores is20 to 99; however, the actual range of subscores forany test or test edition may be smaller than 20 to 99.Subject Test score interpretive information is providedin Interpreting Your GRE Scores, which you will receivewith your GRE score report, and on the GRE Web siteat www.gre.org/codelst.html.

Content of the ComputerScience Subject TestThe test consists of about 70 multiple-choicequestions, some of which are grouped in sets andbased on such materials as diagrams, graphs, andprogram fragments.

The approximate distribution of questions in eachedition of the test according to content categories isindicated by the following outline. The percentagesgiven are approximate; actual percentages will varyslightly from one edition of the test to another.

I. SOFTWARE SYSTEMS ANDMETHODOLOGY — 40%A. Data organization

1. Data types2. Data structures and implementation

techniquesB. Program control and structure

1. Iteration and recursion2. Procedures, functions, methods, and

exception handlers3. Concurrency, communication, and

synchronizationC. Programming languages and notation

1. Constructs for data organization andprogram control

2. Scope, binding, and parameterpassing

3. Expression evaluation


D. Software engineering1. Formal specifications and assertions2. Verification techniques3. Software development models, patterns,

and toolsE. Systems

1. Compilers, interpreters, and run-time systems2. Operating systems, including resource

management and protection/security3. Networking, Internet, and distributed systems4. Databases5. System analysis and development tools

II. COMPUTER ORGANIZATION ANDARCHITECTURE — 15%A. Digital logic design

1. Implementation of combinational andsequential circuits

2. Optimization and analysisB. Processors and control units

1. Instruction sets2. Computer arithmetic and number representation3. Register and ALU organization4. Data paths and control sequencing

C. Memories and their hierarchies1. Performance, implementation, and management2. Cache, main, and secondary storage3. Virtual memory, paging, and segmentation

D. Networking and communications1. Interconnect structures (e.g., buses,

switches, routers)2. I/O systems and protocols3. Synchronization

E. High-performance architectures1. Pipelining superscalar and out-of-order

execution processors2. Parallel and distributed architectures

III. THEORY AND MATHEMATICALBACKGROUND — 40%A. Algorithms and complexity

1. Exact and asymptotic analysis of specificalgorithms

2. Algorithmic design techniques (e.g., greedy,dynamic programming, divide and conquer)

3. Upper and lower bounds on the complexityof specific problems

4. Computational complexity, including NP-completeness

B. Automata and language theory1. Models of computation (finite automata,

Turing machines)2. Formal languages and grammars (regular

and context free)3. Decidability

C. Discrete structures1. Mathematical logic2. Elementary combinatorics and

graph theory3. Discrete probability, recurrence relations,

and number theory

IV. Other Topics — 5%Example areas include numerical analysis, artificialintelligence, computer graphics, cryptography,security, and social issues.

Note: Students are assumed to have a mathematicalbackground in the areas of calculus and linearalgebra as applied to computer science.

Preparing for a Subject TestGRE Subject Test questions are designed to measureskills and knowledge gained over a long period of time.Although you might increase your scores to someextent through preparation a few weeks or monthsbefore you take the test, last-minute cramming isunlikely to be of further help. The following informa-tion may be helpful.

A general review of your college courses isprobably the best preparation for the test. How-ever, the test covers a broad range of subjectmatter, and no one is expected to be familiarwith the content of every question.

▪


� Use this practice book to become familiar withthe types of questions in the GRE ComputerScience Test, paying special attention to thedirections. If you thoroughly understand thedirections before you take the test, you will havemore time during the test to focus on the ques-tions themselves.

Test-Taking StrategiesThe questions in the practice test in this book illus-trate the types of multiple-choice questions in the test.When you take the test, you will mark your answers ona separate machine-scorable answer sheet. Total test-ing time is two hours and fifty minutes; there are noseparately timed sections. Following are some generaltest-taking strategies you may want to consider.

� Read the test directions carefully, and work asrapidly as you can without being careless. Foreach question, choose the best answer from theavailable options.

� All questions are of equal value; do not wastetime pondering individual questions you findextremely difficult or unfamiliar.

� You may want to work through the test quiterapidly, first answering only the questions aboutwhich you feel confident, then going back andanswering questions that require more thought,and concluding with the most difficult questionsif there is time.

� If you decide to change an answer, make sure youcompletely erase it and fill in the oval corre-sponding to your desired answer.

� Questions for which you mark no answer or morethan one answer are not counted in scoring.

� As a correction for haphazard guessing, one-fourth of the number of questions you answerincorrectly is subtracted from the number ofquestions you answer correctly. It is improbablethat mere guessing will improve your scoresignificantly; it may even lower your score.If, however, you are not certain of the correctanswer but have some knowledge of the question

and are able to eliminate one or more of theanswer choices, your chance of getting the rightanswer is improved, and it may be to your advan-tage to answer the question.

� Record all answers on your answer sheet. Answersrecorded in your test book will not be counted.

� Do not wait until the last five minutes of atesting session to record answers on youranswer sheet.

What Your Scores MeanYour raw score–that is, the number of questions youanswered correctly minus one-fourth of the numberyou answered incorrectly–is converted to the scaledscore that is reported. This conversion ensures that ascaled score reported for any edition of a Subject Testis comparable to the same scaled score earned on anyother edition of the same test. Thus, equal scaledscores on a particular Subject Test indicate essentiallyequal levels of performance regardless of the testedition taken. Test scores should be compared onlywith other scores on the same Subject Test. (Forexample, a 680 on the Computer Science Test is notequivalent to a 680 on the Mathematics Test.)

Before taking the test, you may find it useful toknow approximately what raw scores would be requiredto obtain a certain scaled score. Several factors influ-ence the conversion of your raw score to your scaledscore, such as the difficulty of the test edition and thenumber of test questions included in the computationof your raw score. Based on recent editions of theComputer Science Test, the table on the next pagegives the range of raw scores associated with selectedscaled scores for three different test editions. (Notethat when the number of scored questions for a giventest is greater than the range of possible scaled scores,it is likely that two or more raw scores will convert tothe same scaled score.) The three test editions in thetable that follows were selected to reflect varyingdegrees of difficulty. Examinees should note that futuretest editions may be somewhat more or less difficultthan the test editions illustrated in the table.


Range of Raw Scores* Needed toEarn Selected Scaled Scores on

Three Computer Science Test EditionsThat Differ in Difficulty

Raw Scores

Scaled Score Form A Form B Form C800 55 48-49 45700 39 31 28-29600 23 19 16500 7 6-7 4Number of Questions Used to Compute Raw Score

70 70 69

*Raw Score = Number of correct answers minus one-fourth thenumber of incorrect answers, rounded to the nearest integer.

Examples of Ways to Earn a Scaled Scoreof 700 on the Edition Labeled as “Form A”

Number ofQuestions Questions Questions Questions UsedAnswered Answered Not to Compute

Raw Score Correctly Incorrectly Answered Raw Score39 39 0 31 7039 42 11 17 70

39 45 23 2 70

For a particular test edition, there are many ways toearn the same raw score. For example, on the editionlisted above as “Form A,” a raw score of 39 would earna scaled score of 700. Below are a few of the possibleways in which a scaled score of 700 could be earnedon that edition.


Practice TestTo become familiar with how the administration will be conducted at the testcenter, first remove the answer sheet (pages 53 and 54). Then go to the backcover of the test book (page 48) and follow the instructions for completing theidentification areas of the answer sheet. When you are ready to begin the test,note the time and begin marking your answers on the answer sheet.


Scoring Your Subject TestComputer Science Test scores typically range from 520to 800. The range for different editions of a given testmay vary because different editions are not of preciselythe same difficulty. The differences in ranges amongdifferent editions of a given test, however, usually aresmall. This should be taken into account, especiallywhen comparing two very high scores. In general,differences between scores at the 99th percentileshould be ignored. The score conversion table onpage 51 shows the score range for this editionof the test only.

The worksheet on page 50 lists the correct answersto the questions. Columns are provided for you to markwhether you chose the correct (C) answer or anincorrect (I) answer to each question. Draw a lineacross any question you omitted, because it is notcounted in the scoring. At the bottom of the page,enter the total number correct and the total numberincorrect. Divide the total incorrect by 4 and subtractthe resulting number from the total correct. This is theadjustment made for guessing. Then round the result tothe nearest whole number. This will give you your rawtotal score. Use the total score conversion table to findthe scaled total score that corresponds to your rawtotal score.

Example: Suppose you chose the correct answers to38 questions and incorrect answers to 22. Dividing 22by 4 yields 5.5. Subtracting 5.5 from 38 equals 32.5,which is rounded to 33. The raw score of 33 corre-sponds to a scaled score of 670.


Worksheet for the Computer Science Test, Form GR9629 OnlyAnswer Key and Percentages* of Examinees

Answering Each Question Correctly

Correct (C)

Incorrect (I)

Total Score:

C – I/4 = ____________

Scaled Score (SS) = ____________

* The P+ column indicates the percentage of Computer Science Test examineesthat answered each question correctly; it is based on a sample of December1996 examinees selected to represent all Computer Science Test examineestested between October 1, 1993, and September 30, 1996.

QUESTION TOTALNumber Answer P + C I

QUESTION TOTALNumber Answer P + C I

1 C 642 E 693 E 814 E 825 D 88

6 E 787 D 768 A 789 A 70

10 D 83

11 D 4312 D 6513 B 6914 C 3915 C 52

16 D 5617 D 7618 C 6919 A 6720 D 76

21 B 2122 C 6423 D 7024 B 2825 B 42

26 C 7227 E 6828 D 6429 C 5230 A 64

31 A 5632 C 4833 A 8334 A 3935 D 26

36 C 5437 A 2538 B 7039 B 2940 B 46

41 C 3342 E 6143 B 6244 B 4945 E 60

46 B 6047 B 7448 A 3349 D 3250 B 30

51 A 4752 C 4153 A 2054 E 5755 C 35

56 A 5657 B 4358 D 1759 B 4560 D 28

61 B 2462 D 4063 E 2564 D 2965 C 45

66 C 2267 E 4268 B 3969 E 2270 C 45


Score Conversions and Percents Below*For GRE Computer Science Test, Form GR9629 Only

TOTAL SCORE

Raw Score Scaled Score % Raw Score Scaled Score %

70 910 9968-69 900 99

67 890 9965-66 880 99

64 870 9962-63 860 98

61 850 9759-60 840 96

58 830 9556-57 820 94

55 810 9353-54 800 91

52 790 8950-51 780 8648-49 770 85

47 760 8245-46 750 79

44 740 7742-43 730 74

41 720 7139-40 710 67

38 700 64

36-37 690 6035 680 56

33-34 670 5332 660 49

30-31 650 4629 640 42

27-28 630 3925-26 620 35

24 610 3222-23 600 29

21 590 2519-20 580 23

18 570 1916-17 560 17

15 550 1513-14 540 12

12 530 1110-11 520 9

9 510 77-8 500 6

6 490 54-5 480 42-3 470 31 460 20 450 1

*Percentage scoring below the scaled score is based on the performance of 13,161 examinees whotook the Computer Science Test between October 1, 1993, and September 30, 1996. Due tochanges in the test-taking population, the percentile rank data have also changed. To obtaincurrent percentile rank information, visit the GRE Web site at www.gre.org/codelst.html, or contactthe GRE Program.


Evaluating YourPerformanceNow that you have scored your test, you may wish tocompare your performance with the performance ofothers who took this test. Both the worksheet on page50 and the table on page 51 use performance data fromGRE Computer Science Test examinees.

The data in the worksheet on page 50 are based onthe performance of a sample of the examinees whotook this test in December 1996. This sample wasselected to represent the total population of GREComputer Science Test examinees tested betweenOctober 1993 and September 1996. The numbers inthe column labeled “P+” on the worksheet indicatethe percentages of examinees in this sample whoanswered each question correctly. You may use thesenumbers as a guide for evaluating your performance oneach test question.

The table on page 51 contains, for each scaled score,the percentage of examinees tested between October1993 and September 1996 who received lower scores.Interpretive data based on the scores earned by exam-inees tested in this three-year period were used byadmissions officers in the 1997-98 testing year. Thesepercentages appear in the score conversion table in a

column to the right of the scaled scores. For example, inthe percentage column opposite the scaled score of 730is the number 74. This means that 74 percent of theGRE Computer Science Test examinees tested betweenOctober 1993 and September 1996 scored lower than730. To compare yourself with this population, look atthe percentage next to the scaled score you earned onthe practice test. Note: due to changes in the test-takingpopulation, the percentile rank data have also changed.To obtain current percentile rank information, visit theGRE Web site at www.gre.org/codelst.html, or contactthe GRE Program.

It is important to realize that the conditions underwhich you tested yourself were not exactly the same asthose you will encounter at a test center. It is impossibleto predict how different test-taking conditions will affecttest performance, and this is only one factor that mayaccount for differences between your practice test scoresand your actual test scores. By comparing your perform-ance on this practice test with the performance of otherGRE Computer Science Test examinees, however, youwill be able to determine your strengths and weaknessesand can then plan a program of study to prepare yourselffor taking the GRE Computer Science Test understandard conditions.

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