Thursday, November 1

Review Session
Tuesday, October 30
5-6:30PM PST
Hewlett 102


Midterm | Solutions | Code (Qt project for testing your answers)

Scores and Graded Exams

How do I find out my score? The scores have been released on Gradescope, a website for grading course materials. If you did not receive an invitation to join Gradescope (please check your spam folder!) please contact the Head TA. Log in to Gradescope to see your midterm score.

If you have questions about exactly what points you missed and why, please look over the grade and markings made by the grader, compare it with our answer key and test project, and then stop by office hours or contact your Section Leader if you still have any questions.

The statistics of the exam scores (rounded to the nearest whole number, out of 120) were as follows:

Mean: 98

Median: 103

Here is a histogram of the exam scores (out of 120):

Midterm Histogram

Regrade Policy

We work hard to grade consistently and correctly, but sometimes we make mistakes in grading. If you believe part of your exam was incorrectly graded, please first download the Qt Creator project linked to above and run your answer. This is the easiest way to test your code. If, after running your code, you still believe your grade is incorrect, submit a regrade request online via Gradescope (first view the question in your exam, and submit a regrade for that question on that page). Regrade requests need to point out the aspect of the problem that was correct, but for which points were taken off. We use a detailed rubric to grade exams, so simply requesting that an incorrect answer "should be worth more points" is not likely to result in additional points. You must also submit Qt unit test output for the given problem (if applicable), and a copy of your code (if needed, with any minor syntax errors corrected), and any other necessary code/content so that we can run and evaluate your code.

You must provide all the required information listed above and in the regrade request form in order for us to review your regrade request. Also, we reserve the right to re-grade the whole exam to make sure there are no other grading issues present - this may result in a lower total score.

All midterm regrade requests must be submitted within 7 days of the date when exam scores were posted. Specifically, all regrade requests must be submitted by 1:30PM on Monday, November 12, 2018.


Note: the practice BlueBook exam is configured with an infinite time limit. You cannot close BlueBook and come back to work on the exam later - you must complete it in one sitting. You cannot submit practice exams - if you'd like to check your answers, leave BlueBook open while you do so. Note that for security reasons, BlueBook disables copy/pasting into or out of BlueBook.


Based on a handout by Brahm Capoor

BlueBook is a program that can administer electronic exams distributed in a special file format.

We provide versions of BlueBook for both macOS and Windows operating systems. If you have a laptop that does not have one of these operating systems or you are unable to install applications on your laptop for any reason (for instance, it is a work or borrowed laptop), please contact the instructor.

Once you have downloaded the installer file, install BlueBook wherever you wish on your computer. If you're using a Mac and you get an error saying that the Disk Image is from an unidentified developer, open up the installer file in your finder, and right click it and select "Open."" The same window will pop up, but this time you'll have a chance to open it anyway. On Windows, if you get a message that says, "Windows protected your PC," you can click on "More info" and then "Run anyway."

BlueBook itself does not come with any exams but is rather just an application used to take exams. Your exams, including practice exams, will be distributed as .json files which your course staff will upload to the course website. These exam files are encrypted and cannot be opened without a password, which will be provided to you at the start of the exam. Download these .json files and keep them wherever you wish on your computer. The practice exam materials have also been provided in this format, so you can get familiar with the process.

Once you have BlueBook installed and an exam downloaded, begin by opening BlueBook. On a Mac, if you get a message saying that you were blocked from opening the app for security reasons, browse to the app in the Finder, right click it and select "Open."" The same window will pop up, but this time you'll have a chance to open it anyway. The app should go full screen and allow you to choose the exam file you downloaded earlier. Click the folder icon on the right of the screen and navigate to the .json file and click ‘ok’, followed by ‘Load Exam’. At this point, you’ll be brought to the Exam Start Screen. Fill out your details on this screen, fill in the password and click ‘Start Exam’.

You’ll then be brought to the main Exam View, which allows you to go back and forth between all the questions for the duration of the exam. You can navigate between questions using the toolbar at the top of the window. The text editor provided to you will have syntax highlighting, bracket completion and automatic indenting, but will not allow you to compile your code. The exam will end automatically after the specified duration ends.

We know that BlueBook is not the same as working with a compiler as you do in Qt Creator, and we account for that in how we design and grade the exam. We are assessing your ability to think logically and use appropriate problem-solving techniques. We expect you to express yourself in reasonably correct C++, but we will be lenient with errors that are syntactic rather than conceptual.

When you are done with your exam – or time has run out – you can begin the submission process for the exam. Do so by clicking the blue ‘Submit’ button in the toolbar. Once time runs out, this process automatically starts. Beginning submission is an irreversible decision, so make sure that you’re confident you’re ready to turn your answers in. Once you confirm that you want to submit, the BlueBook window will shrink and allow you to turn on your internet in order to submit the exam. Importantly, we verify your identity while submitting, so please make sure to have your two-step authentication device with you. Once your submission is successful, you will see a message with a green check mark and a confirmation code of your exam submission, which you should keep for your records in case any issues arise later. At this point, feel free to close BlueBook. Congratulations! You’re done with the exam!

Some final notes about BlueBook:


What to Bring

The exam is on your computer. You should bring:

Material Covered

The midterm will cover all material up to and including unit testing on Monday 10/22. This includes the following concepts listed below. Note that you may be asked to read code (look at a piece of existing code and answer questions about it, such as writing its output) and/or write code (write a piece of code such as a method or short program that solves a given problem), or answer short written questions.

The following concepts will NOT be tested on the midterm:

Exam Strategies

Hopefully you have been keeping up in lecture and doing well on the assignments, but may be unsure of how to make sure your skills will translate well to the exam setting. The practice midterm will give an idea of what to expect, but we also want to provide some general advice for how to prepare and approach the exam.

The Rationale Behind Computer Exams

You will be taking your exam using software called BlueBook. Electronic exams hold several advantages. For students, writing code on a computer (with syntax highlighting, undo, cut, etc) is a much easier exam experience than writing solutions out by hand. The way in which you are assessed is much closer to the way in which you program. The logistics become much easier for students with disability accommodations. On our end, it makes it a lot easier to make, distribute and grade exams. Instead of using large amounts of paper to to print exam exam, we use 0. Finally, grading handwritten exams is hard and inaccurate. Handwritten exams allow for bias in grading [1] and are inaccurate because we can’t run your programs. Your midterm will still be assessed by a human, but they will be better equipped to understand what you were trying to do.

Great, it’s on a computer! Why can’t I run my program? In a time-restricted situation, immediate feedback from the compiler can be more of an impediment than an advantage. Imagine this: you read the first problem, have a good idea of how to solve it, write your solution, and trace its operation and feel good. You compile and test it. Suppose it exhibits a bug—even though it may only be a minor issue, you can see your answer is wrong—so you hunker down and rework and retest until perfect... even if it takes the whole exam. Bad deal – since you never got to the other problems on the exam! We want you to write your best answer and move on.

How to Prepare for the Exam

"Open textbook" doesn't mean "don't study". The exam is open-textbook; bring along the course textbook. We don’t expect you to memorize minute details and the exam will not focus on them. However, this doesn’t mean you shouldn’t prepare. There certainly isn’t enough time during the exam to learn the material. To do well, you must be experienced at working through problems efficiently and accurately, and using relevant programming patterns, without needing to repeatedly refer to your resources.

Practice, practice, practice. A good way to study for the programming problems is to take a problem (lecture or section example, chapter exercise, sample exam problem, CodeStepByStep problem) and write out your solution under test-like conditions (e.g., in a text editor without compiling, not in Qt Creator, with a short amount of time). Don't fall into the trap of just practicing your exam problems in Qt Creator. The computer compiles your code and provides immediate feedback that you won't have on the real exam. You want to practice under real exam conditions to become comfortable writing code in a timed setting. This is much more valuable than simply reviewing the practice materials, looking at the answers, and making sure you understand why they are correct - a much different task than having to write the solutions yourself.

Get your questions answered. If there is a concept you’re a bit fuzzy on, or you’d like to check your answer to something, or you wonder why a solution is written a particular way, swing by the LaIR/CLaIR, come to office hours, find Nick before/after any lecture, or post on Piazza; we are happy to help.

How to Take the Exam

Scan the entire exam first. Quickly peruse all questions before starting on any one. This allows you to “multitask” — while working on one problem, your mind can be brainstorming strategies or ideas for another problem in the background. You can also sketch out how to allocate your time between questions in the first pass. Speaking of which...

Spend your time wisely. Don’t get stuck on any particular problem. There is much opportunity for partial credit, so it’s better to make good efforts on all problems than to perfect an answer to one, leaving others untouched.

Consider the point value of each question. Divide the total minutes by the total number of points to figure the time per point and use that as guide when allocating your time across the problems. You may want to reserve a little time for checking your work at the end as well.

Leverage the materials you bring with you. If you know of a method/class in the textbook that would help (for example, from an included sample problem or from sample code - this does not pertain to code in the Stanford Libraries such as getWidth(), setColor, etc.), you can simply cite what section/chapter it is from and use it. You do not need to rewrite it.

Style and decomposition are secondary to correctness. Unlike for the assignments, for an exam, unless a question explicitly says otherwise, your responses will only be graded on functionality. Decomposition and style are thus somewhat de-emphasized. However, good design may make it easier for you to get the functionality correct and require less code, which takes less time and has fewer opportunities for errors. Moreover, when a solution is incorrect, good stylistic practices such as commenting may help us determine what you were trying to do and award partial credit.

Answer in pseudo-code, but only if you must. If the syntax of C++ is somehow in your way, you can answer in pseudo-code ("code-like English"). In occasional cases, this may result in a small amount of partial credit. There is a wide variation in the scoring for pseudo-code. Some pseudo-code is vague and content-less and does little more than restate the problem description, and thus is not worth any points. The more details it provides, the better. But truthfully, very good pseudo-code contains so much information that it typically would have been easier and more concise to just write in C++ in the first place.

Pay attention to specific instructions. A problem statement may include detailed constraints and hints. You may want to underline or highlight these instructions to be sure you don’t overlook them. These constraints are not there to make things more difficult; typically we are trying to guide you in the direction of a straightforward and simple solution. If you disregard these instructions, you are likely to lose points, either for not meeting the problem specification or for errors introduced when attempting a more difficult alternative.

Syntax is not that important if it is clear what you mean. We won't trouble you about most small syntax errors (forgetting semi-colons, misspellings, etc.) as long as your intentions are clear. Having said that, if your syntax errors cause ambiguity, we might not get the correct meaning. For example, if we see a for statement followed by two lines, where both lines are vaguely indented or a third line has been added in after the fact, but you forgot curly braces, we may be confused. If there are braces around all the lines, it will be clear you intended both to be a part of the loop body, but without the braces, we can’t be sure and it may make your answer incorrect.

Comment out abandoned attempts rather than erasing them. As it usually turns out on a CS exam, you will have false starts on a problem — you try one strategy and hit a dead end. You try something else and then realize you actually were closer to the right solution the first time. If you haven’t erased your first attempt, you can always go back to it. Once you work out a better answer, comment out your earlier attempt. When you comment out work, please direct us to where you have written the solution you want graded instead. If you forget to comment out your bad attempt and hence appear to have two answers, we reserve the right to pick which one to grade.

Save a little time for checking your work. Before handing in your exam, reserve a few minutes to go back over your work. Check for missing initialization/return statements, correct parameters passed to functions, etc. We try not to deduct points for minor things if it is obvious what you meant, but sometimes it is difficult to decipher your true intention. You might save yourself a few lost points by tidying up the details at the end.

Download the exam ahead of time. The exam file that you open in BlueBook will be posted on the course website in advance of the exam; we will also send out an email when it is available. Download the encrypted exam before you come to the exam so that you are ready to go when the test starts. We will provide a password when the test starts that unlocks the exam.

Prepare your laptop. We will have limited outlets available for those who absolutely need them. Come with a laptop that has enough battery for the full exam. If you need battery it would be useful for you to bring your own power strip. Make sure your computer isn’t just about to run out of memory.

Final Thoughts

Always remember why you are at school. Learning and education tend to be a more fulfilling goal than just high grades. If you work hard, study lots and feel good about your understanding of computer science, that is an achievement to be proud of in itself — regardless of how many points you get relative to the other students in the class. Remember that computer science is not an easy endeavor, even for experienced computer scientists.

You can do it!