CE151-4-AU UNIVERSITY OF ESSEX. Sample Examination Questions 2011 INTRODUCTION TO PROGRAMMING

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1 CE151-4-AU UNIVERSITY OF ESSEX Sample Examination Questions 2011 INTRODUCTION TO PROGRAMMING This paper contains questions from the first half of the CE112 papers from 2009 and 2010, adapted to Python. Questions from the past papers that cannot be translated into Python have been omitted. The 2009 and 2010 papers were three-hour examinations comprising 10 questions each worth 10% of the paper. Such questions would be worth 15% of a two-hour paper; hence the percentages shown in the original papers have been multiplied by 1.5 [ The marks for question 5 from 2009 do not correspond to the marks in the original paper since the modification from C to Python required more substantial changes than the other questions; furthermore the marks for this question do not add up to 15%. ] The 2011 paper will contain five questions each worth 15% and a longer question worth 25%. A sample longer question is provided at the end of this paper Please do not leave your seat unless you are given permission by an invigilator. Do not communicate in any way with any other candidate in the examination room. Do not open the question paper until told to do so. All answers must be written in the answer book(s) provided. All rough work must be written in the answer book(s) provided. A line should be drawn through any rough work to indicate to the examiner that it is not part of the work to be marked. At the end of the examination, remain seated until your answer book(s) have been collected and you have been told you may leave.

2 CE151-4-AU 2 QUESTIONS BASED ON CE Question 1 Briefly describe what is meant by a syntax error and a runtime error. The following program should read a sequence of integers from the keyboard and terminate when the total of the numbers that have been read is greater than 500, outputting the average value so far after the each input. However, there are two errors that will be detected by the IDLE syntax-checker and one that will cause failure at runtime and another that will cause the program to behave incorrectly. For each of the four errors, give - the number of the line of code where it occurs - the kind of error in that line of code - the way in which the error should be corrected [12%] 01 count = 0 02 finished = False 03 total = 0 04 while finished: 05 number = int(input("enter a number: )) 06 total = total + number 07 print("current average is ", total / count); 08 if total> finished = True 10 count = count + 1;

3 3 CE151-4-AU Question 2 What is the value of each of the following Python expressions? (i) 7 // 3 (ii) 7 / 2 (iii) 2 * a (iv) 5.3 > 5 (v) 1==1 or 2>1 and 1>2 (c) What is the value of sum after the following code has been executed? i = 0 sum = 0 while i < 9: if i%4 == 0: sum = sum + i i = i + 2 Rewrite the code fragment from part using a for loop without using any break statements and without introducing any more variables; [4.5%]

4 CE151-4-AU 4 Question 4 Write a full definition for a Python function called compare, which takes as arguments two strings s1 and s2 and an integer n, and returns the value True if the first n characters in the string s1 are the same as the first n characters in the string s2 and returns the value False otherwise. You may assume that both strings have at least n characters. [6%] Write a full definition for a function called minsum, which takes as an argument a list of lists of numbers, calculates the sum of the values in each of the lists and returns the smallest such sum. [ For example, if the argument was [[1, 4, 0, 2], [2, 5, 1, 3], [3, 6, 2, 4]] the sums would be 7, 11, and 15, so the value returned should be 7. ] [9%]

5 5 CE151-4-AU Question 1 QUESTIONS BASED ON CE Briefly describe what is meant by a syntax error and a type error. The following Python program contains one error that will be detected by the IDLE syntax-checker and three that may cause failure at runtime. For each of the four errors, give - the number of the line of code where it occurs - the kind of error in that line of code - the way in which the error should be corrected [12%] 01 count = 0 02 sum = 0 03 finished = False 04 while not finished: 05 number = input("enter a number: ") 06 if number<0: 07 finished = true 08 else: 09 sum = sum + number 10 print("average ="; sum / count)

6 CE151-4-AU 6 Question 3 (part) (c) (d) Not relevant to Python. What is the value of sum after the following code has been executed? sum = 0 for i in range(0, 18, 3): if i%6 == 0 : sum = sum + i Rewrite the code fragment from part using a while loop without using break statements and without introducing any more variables; Not relevant to Python. [4.5%] [6%]

7 7 CE151-4-AU Question 4 Provide a full Python function definition for a function isuppercasevowel, which takes as an argument a single-character string and which returns the value True if the character supplied as an argument is an upper case vowel (i.e. A, E, I, O or U) and returns the value False otherwise. Not relevant to Python (c) Write a statement that initialises the value of a variable b to be a list of 5 integers in which all the elements have an initial value of 2, without mentioning the number 5. [1%] (d) Write a statement that initialises the value of a variable c to be an list of 100 integers in which the first five elements have an initial value of 1, and the remainder have an initial value of 0. [You must not explicitly use 95 zeroes!] [2%] (e) Write a full definition for a function called maxsum which takes as an argument a list of lists of numbers, calculates the sum of the values of each list and returns the largest such sum. [7.5%]

8 CE151-4-AU 8 Question 5 Consider the following Python function. def swap(a, b): temp = a a = b b = temp (i) Explain why after a call of the form swap(x,y) the values of the variables x and y will be unaltered. (ii) Write a single statement that will swap the values of the variables x and y without using a temporary variable. An outline for a Student class is defined as follows. class Student(object) : def init (self, name, regnum, postgrad) : self.name = name self.regnum = regnum self.postgrad = postgrad def showstudent(self) : You should assume that the name is a string, the registration number is an integer and the postgrad attribute is a boolean value indicating whether the student is a postgraduate. (i) Provide a complete body for the method showsudent which should display on one line the name, registration number and postgraduate status of the student supplied as an argument in the following format. Name: Fred Smith; Reg Number: 12345; Postgrad: no (ii) Write a full function definition for a function showundergrads which takes as an argument a list of objects of type Student and makes use of the showstudent method to display details of all of the undergraduates in the list [4%]

9 9 CE151-4-AU Question 6 SAMPLE LONGER QUESTION A file containing data about a collection of students has the following format. Fred Smith CSEE Jim Brown CSEE Ann Simpson Biology Each line contains a first name, a second name, a registration number, a year and a department. Write a complete Python program that will input the contents of the file into a list of tuples, and output each of the following full details of the student sorted by registration number (in a neatly formatted table) the names of all students with a year of less than 3 the number of people in each department The output for the data shown above should be Ann Simpson Biology Fred Smith CSEE Jim Brown CSEE Fred Smith Ann Simpson CSEE 2 Biology 1 You may assume that no name occupies a total of more than 20 characters and all registration numbers have five digits. The filename should be obtained from the user; if the file does not exist the program should display an appropriate message and ask the user to supply another filename. END OF PAPER CE AU