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Computer Science


CS 420/520 Object-Oriented Programming

Course Description

Course Overview



Academic Integrity Policy

PSU Student Code of Conduct

Class Piazza Site

PSU Grace Resources

Pomona College Grace Resources:

Grace Code

Slides from Class


Spring Quarter 2019

Monday and Wednesday, 14:00–15:50 in FAB 044 (in the basement, NE corner of FAB)

CRN 64841 (CS 420) Restricted to: MCECS; JR SR PB.
CRN 64842 (CS520).  There is a waitlist; come to the first class anyway.

Andrew Black
email: black
telephone: 503 725 2411 

Prof Black will hold office hours in FAB 115-10 on Wednesday from 16:00 to 17:00.  He's available anytime on Piazza.

Shikha Shah
email: shikha2 (at)


Familiarity with programming is assumed, as well as with the basic terminology of object-orientation.  However, proficiency with object-oriented concepts is not assumed, and students who have experience with Java or C++ should be prepared to unlearn some of what they think they know.  Prior experience with Grace is not required. The class assumes a working knowledge of discrete mathematics, machine organization, and compilation.  A working knowledge of JavaScript may be useful for some projects.


Course Description

The objective of this course is to teach students to program well in an object-oriented style. The focus is more on object-oriented design and programming than on a particular language and its niceties. The course will use the Grace programming language, a new and very simple language that allows the programmer to construct objects directly. Using Grace permits the course to be focused on concepts rather than on navigating the intricacies of a language definition.  Samples of other languages, such as Smalltalk, Ruby and JavaScript may be included.

Topics covered will include responsibility-driven design, test-driven development, refactoring, code reading, reuse, parametrization, inheritance and programming patterns.

Specific Learning Objectives

On completion of this course, students should be able to:

  1. Design a group of collaborating objects to implement a given set of requirements;
  2. Assign the responsibilities for the actions implied by the requirements to the appropriate objects;
  3. Partition these responsibilities into appropriately named methods;
  4. Write definitions for the classes that can be used to generate these objects;
  5. Deduce the data necessary to implement the requirements, and partition that data among the objects
  6. Define appropriate instance variables to store these data;
  7. Create superclasses and superobjects in order to share common code;
  8. Arrange the concrete and abstract classes in an appropriate hierarchy;
  9. Write tests for methods, classes and objects;
  10. Explore existing objects, classes and methods in the Grace programming environment;
  11. Read, write, edit, test, share and debug Grace code; and
  12. Create Grace modules containing their programs and package them for reuse.



I recommend that you come to class, that you participate actively, and that you take notes. The act of taking notes (even if you never look at them again) is a powerful learning aid. I will generally make any visual aids, code samples, etc. that I used in class available on the web, but these are not a substitute for being in class and taking notes. If you do have to miss a class, say because of illness or work-related travel, you are responsible for getting notes and finding out what went on in class from another student.

Reading Assignments

Reading listed in the syllabus for each week should be completed before coming to class. I may check on the completion of reading assignments by various means: oral or written quizzes in class, written summaries, discussion (web-based or in class), etc. Anything in a reading assignment is fair game for a quiz question.

Programming Assignments

Print-outs of your assignment submissions are due at the start of class. On-line submissions are due before the start of class.


I do sometimes make mistakes! If you believe that I have not graded your assignment according to the published grading scheme, please let me know in writing (email counts as writing!) within 1 week of the assignment being returned to you. Be specific as to why you think that my grading is inconsistent. I will then re-grade the whole assignment; the second grading will stand, whether it is higher or lower than the original grading.


If you are a student with a disability in need of academic accommodations, you should first register with the Disability Resource Center, and then notify the instructor to arrange for support services.

Makeup Exams

If you have a medical or a family emergency and must miss an exam, let me know, if at all possible before the exam, and I will work with you to find an alternative. Other reasons for absence such as scheduled travel are not emergencies and are not cause for a make-up.

Passing the Course

Every assignment in the course is connected to a learning objective. It is therefore important that you make an honest attempt to complete them all. A score of less than 30% on any assignment indicates that you have not met this condition, and is sufficient cause for failing the course. That means an F, at the discretion of the instructor.

Academic Integrity

Students are at university for two reasons: to learn stuff, and to gain a credential. Because the credential is important to many of our students, part of my role as a professor is to make sure that it has value. This means ensuring that a passing grade is awarded only to those students who have mastered the material in my course.

I have every sympathy for those who have difficulty with the material and seek the assistance of the instructor, the TA or their fellow students. I have no sympathy at all for those who decide that the fastest way to a degree is to cheat. I have been responsible for having cheating students dismissed from the university in the past, and I will not hesitate to seek to have cheaters dismissed in the future.

The most common form of academic dishonesty — cheating — is representing the work of others as your own. In all written material, it is expected that you will use others' work, but when you do so it must be in a way that makes it absolutely clear that someone else's work is being cited, and who is the original author. If you reproduce someone else's work in a way that makes it appear to be yours, you are guilty of plagiarism—in other words, of cheating.

Cheating on an assignment or exam will result in an automatic zero grade for that piece of work, and the initiation of disciplinary action at the University level.

Cheating and collaboration

I encourage collaboration on certain assignments; I will not tolerate cheating. Where is the line between these activities?

First, if an assignment is explicitly set up as a team assignment, you are of course allowed — indeed, required — to collaborate with the members of your team. In this case I will generally require only one completed piece of work to be turned in from the team as a whole.

For individual assignments, I encourage you to talk about the problem with your fellow students. During such discussion, you may even write something, perhaps the code of a critical method, as a group. If you do this, there is a danger that you might reproduce that group work as if it were your own. To guard against this danger, do the following: after the group session, destroy all the notes and code fragments that you may have brought away with you. Then go and do something else for an hour or two: go for a walk or a bike ride, play your favorite sport, go to the gym: do something to flush your short-term memory. Then sit down with a blank sheet of paper or a blank workspace and start work on your own solution. If you have a photographic memory or otherwise won't be able to forget what you have seen someone else write, then don't participate in collaborative problem-solving sessions.

If I see the same code or writing assignment from two or more students I will take this as evidence that these guidelines have been ignored, and will assign a grade of zero to all of the students involved.

Course Grading

Grade Distribution: 50% on homework assignments, 40% on the class project, and 10% on attendance and class participation. Your participation will be used to judge whether you are keeping up with the reading assignments.

Most recently modified sometime in the past

Andrew P. Black