PROBLEM 1 : (Vocabulary: 12 points) For each of the words/phrases below, circle the denition that is the best description as it pertains in the contex

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1 Test 1: CPS 53.2 Owen Astrachan October 6, 1993 Name: Honor code acknowledgement (signature) Problem 1 value 12 pts. grade Problem 2 14 pts. Problem 3 5 pts. Problem 4 6 pts. Problem 5 9 pts. Problem 6 10 pts. Problem 7 10 pts. Problem 8 15 pts. Problem 9 15 pts. Problem 10 extra TOTAL: 10 pts. 96 pts. 1

2 PROBLEM 1 : (Vocabulary: 12 points) For each of the words/phrases below, circle the denition that is the best description as it pertains in the context of computer science, programming, and C/C I/O streams (a) a thought process in which ideas are immediately transformed to programs (b) standard classes that are used for input and output of both built-in and user-dened types (c) a contiguous collection of homogeneous elements supporting random access 2. formal parameters (a) the parameters that occur in a function call as opposed to in a function header (b) the parameters that occur in a function header as opposed to in a function call (c) parameters with well-dened names that are indicative of their purpose 3. loop guard (a) the boolean expression whose truth determines if a loop body is executed (b) a programming device that protects against innite loops (loops that execute forever) (c) a term used to describe the evaluation of the expression (a && b) in which bisnot evaluated if a is false. 4. return statement (a) the line in a Makele that returns control to the user (b) a statement that returns (a value) from a function (c) the hidden statement that the compiler inserts in a for loop to ensure that the loop begins execution again after the increment part of the for loop is executed PROBLEM 2 : (Header les: 14 points) For each function, type, or class on the left, list the header le needed for its use. All header les are not used and a header le can be listed more than once. If no header le is needed (e.g., the type is built-in) put 0. sqrt 0. no header le needed cin 1. iostream.h String 2. math.h pow 3. String.h cout 4. heart.h double 5. nput.h Heart 6. ctype.h char 7. stdio.h 2

3 PROBLEM 3 : (Heart Monitor: 5 points) In the program you wrote that sensed a simulated heart and administered a shock if the heart was beating too rapidly or too slowly, a message similar to the following was printed: heart shocked after 20 senses However, if a \bad" voltage reading occurred (outside the range,10::10), and the program heartmon.cc ignores such bad readings in determining the period during which zero-crossings are counted, a message might appear such as heart shocked after 23 senses where the 23 indicates that the heart was sensed 23 times, but your program only acknolwedged 20 as legitimate senses. Explain (briey) why your program could not avoid such counts as 23 being printed even though your program was ignoring these senses in determining zero-crossings. PROBLEM 4 : (Grades: 6 points) The following lines appear in a program designed to compute student grade point averages: gpa = pointtotal/numcourses; cout << "number of courses = " << numcourses << endl; cout << "student GPA = " << gpa << endl; if (gpa >= SUMMA_CUTOFF){ cout << "summa cum laude graduate" << endl; Part A Assume a gpa of 3.75 is needed to graduate summa cum laude, write an appropriate denition for the identier SUMMA_CUTOFF. Part B The registrar notices that only students with 4.0 averages are graduating summa cum laude and that the only gpa's actually printed are 1.0, 2.0, 3.0, and 4.0; i.e., no one has a gpa with a fractional part such as 3.63 the registrar thinks that there is an error in the program. The programmer claims the program is correct because the variable gpa is of type double. The registrar is correct, the program has a small error. Briey describe why the only gpa's printed are 1.0, 2.0, 3.0, and 4.0, and a simple x that will cause \correct" gpa's to be printed. 3

4 PROBLEM 5 : (Debugging: 9 points) The quadratic formula is used to nd roots of quadratic equations of the form ax 2 + bx + c formula is:,b p b 2, 4ac the 2a For example, the roots of the equation x 2 +2x,15 are -5 and 3 (substituting these values for x yields 0) and the formula simplies as:,2 p 2 2, 4(1)(,15) 2(1) =,2 p 64 2 =,2 8 2 =,5 or3 The following C++ function is designed to print the roots of a quadratic equation whose coecients are specied by the parameters a, b, and c; it does not work as intended. void QuadRoots(double a, double b, double c) //precondition: a,b,c, are coefficients of a quadratic equation // which has roots //postcondition: roots of equation ax^2 + bx + c are computed and printed { double discriminant = sqrt(b*b - 4*a*c); double root1 = -b - discriminant/(2*a); double root2 = -b + discriminant/(2*a); cout << "roots are " << root1 << " and " << root2 << endl; Part A: The call: QuadRoots(1,2,-15) should result in the message roots are -5.0 and 3.0 being printed as described above. When run, however, the procedure generates as output roots are -6.0 and 2.0 Briey describe the error in QuadRoot or indicate in the code how to x it so that the correct values will be printed. Part B: On a computer system the call QuadRoots(2,3,4) generates the error message: floating point exception: bus error A programmer adds an output statement just before the denition of root1 as shown below, but no output appears before the error message is printed. cout << "disc = " << discriminant << endl; double root1 = -b - discriminant/(2*a); 4

5 Describe why the error message appears and one possible method for xing the code so that no error message is generated. Part C: It is possible to change the function QuadRoots so that rather than printing the roots, the values of the roots are returned via parameters so that the sequence of statements: QuadRoots(1,2,-15,r1,r2); cout << "roots = " << r1 << " and " << r2 << endl; would result in printing the roots of the equation x 2 +2x,15. Describe the changes in the function QuadRoots that are needed for it to work in this manner. PROBLEM 6 : (Sum: 10 points) You are to complete a code segment that will permit the user to enter integers until the integer 0 is entered. After the numbers are entered the sum of the negative integers entered should be printed. For example: enter a number> 3 enter a number> 4 enter a number> -5 enter a number> 7 enter a number> -2 enter a number> -1 enter a number> 8 enter a number> 0 sum of negative numbers = -8 The code segment is partially given below: int num; cin >> num; while (num!= 0) { cout << "sum of negative numbers = " << negsum << endl; 5

6 PROBLEM 7 : (Change: 10 points) You are to write a function ChangeChar that changes all occurrences of a specic character in a string to another character. For example, if str represents the string \daddy", the call ChangeChar(str,'d','p') would change str so that it represents the string \pappy". Assume that variables of type String support a Length method. Complete the procedure below, be sure all parameters are properly specied. void ChangeChar(,char oldchar, char newchar) 6

7 PROBLEM 8 : (Diving: 15 points) You have been contracted to write a C++ function DiveScore, whose header is given below, to assist in scoring Olympic diving competition. The number of scores that are stored in the array parameter scores is given by the parameter numscores and the diculty factor of the dive is specied by the parameter difactor. The overall score, which is to be returned by the function DiveScore, is computed by throwing out a high and low score, computing the average of the remaining scores, and multiplying this average by the diculty factor. For example, if the scores 5.0, 5.5, 4.5, 5.0, and 5.5 are stored in the array diving as indicated: :::::: for a dive with diculty factor 2.3, then the expression DiveScore(diving,5,2.3) should evaluate to *2.3 = (because the average of 5.0, 5.5, and 5.0 is ). Complete DiveScore below the following header double DiveScore(double scores[], int numscores, double difffactor) // precondition: numscores = number of dive-scores in array scores // postcondition: returns score of dive according to rules of // removing a high and low score, averaging, and // multiplying average by difffactor 7

8 PROBLEM 9 : (15 points) Consider a class StockBroker whose partial implementation is given below: class StockBroker{ private: int numstocks; public: StockBroker(); // constructor // returns current price of stock passed as parameter double CurrentPrice(String); // returns opening price for current trading period of // stock passed as parameter ; double OpeningPrice(String);... For example, the loop below prints the current price of the stock whose name is \IBM". The loop executes until the price of IBM is greater than $80.00 (which might be forever). StockBroker broker; double price = broker.currentprice("ibm"); while (price <= 80.0){ cout << "$ " << price << endl; price = broker.currentprice("ibm"); What to do You are to write a code segment that will be used to monitor a specied stock and to \sell" the stock if its current price is more than twice its opening price. In this problem selling a stock consists of printing a message as shown below and stopping the stock monitoring process. sell stock: Nike current price $ opening price $ However, a current price can be requested no more than 10,000 times during the monitoring process. If more than 10,000 requests are made the monitoring process should stop and a message similar to that below printed. price requests for Nike exceeded 10000, monitoring halted The code you write should consist of appropriate initialization, a loop that gets prices, and a statement that prints a message indicating why monitoring stops as described above. Complete the code segment on the next page. 8

9 StockBroker broker; String name; cout << "enter name of stock "; cin >> name; double openprice = broker.openingprice(name); extra credit on back of page 9

10 PROBLEM 10 : (Extra Credit Heads or Tails 10 points) A Coin class is dened by the declarations below which would appear in the le coin.h class Coin{ ; private: <some fields/methods declared here>; public: Coin(); int Flip(); // the constructor // returns 1 50% of the time, returns 0 50% of the time The code segment below uses the coin object to toss a simulated coin 6 times with sample output as indicated: Coin penny; int k; for(k=0; k < 6; k++){ if (penny.flip() == 1){ else{ cout << "heads" << endl; cout << "tails" << endl; heads tails tails heads tails heads " output Write the function MaxTails whose header is given below. MaxTails is to simulate the tossing of a coin the number of times specied by parameter numtosses and return the longest sequence of consecutive \tails" that are tossed. For example, in the sequence of six tosses shown above, the longest consecutive tails sequence is two. int MaxTails(int numtosses) // precondition: numtosses > 0 // postcondition: returns length of longest sequence // of consecutive tails in numtosses simulated // coin tosses 10

Test 1: CPS 08 Owen Astrachan February 17, 1995 Name: Honor code acknowledgement (signature) Problem 1 Problem 2 Problem 3 Problem 4 Problem 5 Extra T

Test 1: CPS 08 Owen Astrachan February 17, 1995 Name: Honor code acknowledgement (signature) Problem 1 Problem 2 Problem 3 Problem 4 Problem 5 Extra TOTAL: value 8 pts. 12 pts. 10 pts. 10 pts. 12 pts.