ENCM 339 Fall 2017 Lecture Section 01 Lab 5 for the Week of October 16

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1 page 1 of 5 ENCM 339 Fall 2017 Lecture Section 01 Lab 5 for the Week of October 16 Steve Norman Department of Electrical & Computer Engineering University of Calgary October 2017 Lab instructions and other documents for Section 01 of ENCM 339 can be found at Administrative details Each student must hand in their own assignment Later in the course, you may be allowed to work in pairs on some assignments. Due Dates The Due Date for this assignment is 3:30pm Friday, October 20. The Late Due Date is 3:30pm Monday, October 23. The penalty for handing in an assignment after the Due Date but before the Late Due Date is 3 marks. In other words, X/Y becomes (X 3)/Y if the assignment is late. There will be no credit for assignments turned in after the Late Due Date; they will be returned unmarked. Marking scheme A B C D total unmarked 24 marks How to package and hand in your assignments Please see the information in the Lab 1 instructions. Exercise A: Array utility functions A collection of C utility functions is a collection designed to be useful in more than one practical project. The functions are designed, documented, coded, and tested; if the functions pass all the tests, then the files associated with the utility functions can be copied multiple times into different folders for various software application projects.

2 ENCM 339 Fall 2017 Lecture Section 01 Lab 5 page 2 of 5 The tests for individual utility functions are an example of things called unit tests. A unit test is not designed to test an entire application instead, it is designed to test one small component of an application, such as a C function. Unit tests are helpful because they often find defects in small components before the components get used in large applications. If a big application fails because one of its many small components is defective, it can sometimes be very hard to locate the exact cause of the failure. Of course, unit tests are not magic bullets that ensure that components are perfect before components get used. The two main problems are these: Testing a component can find defects, but usually cannot prove that the component will always work correctly. The number of cases that would have to be tested to prove correctness is effectively infinite for all but the very simplest of components. What happens if the unit test code is itself defective? It could then fail to find defects in components, or falsely identify defects when components behave correctly. Nevertheless, spending time to write and run good unit tests is generally a much better strategy than not spending any time at all on unit testing. For a small set of C utility functions, a good unit test plan involves writing unit tests into the.c files that contain the definitions of the utility functions. Download the files array-utils5a.c and array-utils5a.h. Read the files. You should observe that this code obviously provides only a toy collection of utility functions the collection is way too small to be useful, and just barely big enough to serve as an example. Notice that much of the code in array-utils5a.c is surrounded by and #ifdef UNIT_TESTS #endif // #ifdef UNIT_TESTS The code between those two lines will not make it out of the C preprocessor unless the macro UNIT_TESTS is defined. Attempt to build an executable with the command gcc -Wall array-utils5a.c That will fail because no definition of a main function will be found. Try again with gcc -Wall -DUNIT_TESTS=1 array-utils5a.c This should succeed, because the -D option here has the same effect that #define UNIT_TESTS 1 would have at the very beginning the.c file. Run the executable and observe the output. (If you are not working in the ICT 320 lab, you may have to modify the above instructions. If you can t find a way to tell your development tool to define UNIT_TESTS before it starts reading the.c file, just edit in #define UNIT_TESTS 1

3 ENCM 339 Fall 2017 Lecture Section 01 Lab 5 page 3 of 5 at the top of the.c file.) The definitions for is_sorted and all_different are both defective. Make sure you understand what the logic errors are in those definitions are, then rewrite the definitions so that they are correct. The definition for is_arith_seq is missing. Write a correct definition for that function, and add unit tests for it, using the unit tests for is_sorted and all_different as models. Two short paragraphs explaining the logic errors present in the given definitions of the is_sorted and all_different functions; a copy of your final version of array-utils5a.c; Exercise B: Practice with various features of C This exercise is unmarked. It was designed to be review to help you get ready for Quiz 2. Download the file drill5b.c and read it carefully. Make a memory diagram for the second time the program reaches point one. You can check your work against a solution that will be posted no later than Monday evening, October 16. Nothing. Exercise C: Vectors in 3-dimensional space Vectors in 3-dimensional space have many applications in engineering. They also provide an example of an easy-to-understand C structure type. Let s use the following notation for the components of two vectors u and v: u x v x u = u y u z, v = v y v z Then the scalar product of some number k and v is kv x kv = kv y kv z The dot product of u and v is defined to be u v = u x v x + u y v y + u z v z

4 ENCM 339 Fall 2017 Lecture Section 01 Lab 5 page 4 of 5 The sum of u and v is defined to be u + v = u x + v x u y + v y u z + v z And finally, the cross product of u and v is defined to be u v = u yv z u z v y u z v x u x v z u x v y u y v x Download the files vec5c.h, vec5c.c, and main5c.h, and study the code and comments. Build an executable and run it to see if the output is what you expect. Add function prototypes and function definitions in the appropriate files so that functions are available for dot product, sum, and cross product. Then add code to main to call these functions and display the dot product of u and v, the sum of u and v, and the cross product of u and v. copies of your final versions of the.c and.h files; Exercise D: Accessing data in an array of structures Processing student grades using a C program is far from the most convenient way to do that kind of work. However, we ll do that in this exercise to get practice accessing data within structure objects. The fake course we ll consider has ten assignments, numbered 0 through 9. Maximum marks for the assignments are as follows: assignment maximum marks The sum of the maximum marks is 105. Normally, a student s overall assignment mark would therefore be the sum of their own assignment marks divided by 105, then multiplied by 100 to get a percentage. However, a student may have been excused from one or more assignments. In that case, it s not appropriate to divide by 105. For example, if a student were excused from Assignment 8, the overall assignment mark would be calculated as (sum of student s marks)/(105 13) 100%. A fake mark of 1.0 in the class record indicates that a student has been excused from an assignment. Download the file grades5d.c and study the code and comments. Build an executable and run it to see if the output is what you expect. Modify the program so that instead of simply printing a list of names and ID numbers, it prints a list of names, ID numbers, and overall assignment scores.

5 ENCM 339 Fall 2017 Lecture Section 01 Lab 5 page 5 of 5 Here s an example of the expected format for a line of output, for a student who was excused from Assignments 5 and 6: Jones, JJ / 82.0, 87.20% a copy of your final version of grades5d.c;