1.   Getting started

Welcome to CS 15900! One of the three credit hours assigned to this course is devoted to a weekly two-hour lab period. These labs will be an opportunity to learn new material, to review content from previous lectures, and to create new programs in a collaborative environment with your fellow students.

The tasks that follow are designed to help you become familiar with how you will be completing programming assignments in this class - including both lab assignments (which are completed in teams of students) and homework (which are completed individually). The tasks in Lab #0 will be individual as well, but feel free to ask your neighbors, teaching assistant, or Ed for help.

You must understand these instructions in order to be able to complete future assignments, so take your time and revisit these activities as necessary.

2.   Submitting attendance

CS 15900 uses a digital attendance tracking system called the lab manager, where students log their own attendance status to be reviewed by their lab instructor. The lab manager only allows students to submit attendance from ITaP computer workstations located within their lab section room of record during the times in which the lab section is holding class.

Specifically, you can mark yourself as “on-time” beginning 5 minutes before your lab section starts, and up until 5 minutes after it starts. As an example, for a lab section that starts at 9:30 AM, you would be able to mark yourself as “on-time” anywhere between 9:25 AM and 9:35 AM.

After 5 minutes of the class have elapsed, you may only be able to mark yourself as “late”. After the class ends, you will not be able to submit attendance for this assignment at all.

Your lab instructor and lecturer have the ability to override your attendance status if there is a technical issue regarding your ability to access the lab manager, or if you have an excused reason to be late. For all other issues, lab instructors are only allowed to give you one override per semester.

Every lab programming assignment instructions document will contain a link at the top to the lab manager so that you may mark yourself as on-time for the assignment. It is your responsibility to remember to do so.

You can log in to the lab manager and submit attendance for an assignment by clicking the following link. You must log in from an ITaP computer workstation in your lab section’s room.

https://www.cs.purdue.edu/cs159/lab/submit_attendance.php

You should be presented with a screen similar to the following:

Your pending attendance status for each assignment is shown next to the assignment name. Here, a green “On-time” box next to “Lab #0” indicates that we are in the correct room at the correct time. However, the black “Not submitted” box indicates that you have not yet submitted attendance for this assignment.

Click the checkbox next to “Lab #0”, then click the “Submit” button. If the submission was successful, a green confirmation box will appear near the top of the screen indicating as such, and a green “Already submitted” box will replace the black “Not submitted” box in the assignment list.

You will also receive a confirmation email from cs159-wiki@cs.purdue.edu.

By clicking the blue “CS 15900 lab manager” heading you can access the lab manager’s homepage. This includes a link to the page you were just on (“Submit attendance for an assignment”) as well as another link (“View my attendance records”, which you can access from any computer - not just ones in your lab).

3.   Logging into Vocareum

All programming assignments are completed using a website called Vocareum. Your access to Vocareum is controlled by the CS 15900 course on Brightspace - always log in there first if you haven’t already.

Navigate to “Content”, then “Week 1”, then “Assignments”. Open the link that says “Lab #0 (Vocareum)”. Your account with Vocareum will automatically be created.

4.   The student workbench

Clicking the Brightspace links open what is called the “student workbench”. It is from here that you will develop and submit all of your assignments.

The top right side of the screen has several buttons that can be used.

• The four arrow icon will put Vocareum in full-screen mode.

• The “Readme” button opens the lab instructions in the pane on the right hand side of the screen.

  Note

  When you first open the workbench, the instructions are already shown.

• The dash button allows you to minimize or restore the lab instructions, or whatever other content is in that pane.

• The other two buttons will be discussed later in this assignment.

The left hand side of the screen is the interactive terminal - essentially a text-based user interface for the remote computer on which you will be doing your work. Shown below is the terminal command prompt.

The prompt consists of your Purdue username in gold, the current assignment name in blue, and a dollar sign. When you begin typing, the characters you enter will appear after the dollar sign. This is where you can enter commands that the remote computer will perform (or “execute”). The black box indicates the position of your cursor (i.e. where the next character you enter will appear).

5.   Navigating and managing files in a UNIX-like environment

The operating system in which you will be working is Ubuntu, which is based on the Linux kernel. This is a UNIX-like operating system, which is very similar to Apple macOS and very different from Microsoft Windows. All three share the same basic concepts, however: information is stored in “files” and organized into “folders” containing files. In UNIX terminology, folders are more often referred to as directories. These two terms, folders and directories, may be used interchangeably.

When you first open the terminal, you are placed into the directory from which you will be creating, testing, and submitting your assignments, which we will refer to as the workarea. To see which files are in your workarea, you can use the ls command. Type ls, then hit the Enter key to execute the command.

The results of the command (the “output”) appear immediately below the command prompt and the command name that you just typed. In this case, the ls command says that there is a file named round.c in our workarea. After a command finishes executing, the prompt will appear again, indicating that the computer is ready to execute your next command.

Some common UNIX commands include:

cp FILE1 FILE2

Make a copy of FILE1 named FILE2.

mv FILE1 FILE2

Move (i.e. rename) FILE1 to FILE2.

rm FILE

Remove (i.e. delete) the file named FILE. You can specify multiple files separated by spaces.

!DANGER!

You will be asked to confirm that you want to delete the file. Once the file is deleted, it CANNOT be recovered!

6.   Opening the “vi” text editor

A text editor is a program you use in order to edit text-based files. This is similar in concept to Microsoft Word, except that there is no bold, underline, etc. - all of the text in the file is “plain text” (has no formatting).

The vi (pronounced vee-eye) text editor will be the one officially supported by the course. This particular editor has a text-based user interface (TUI) instead of a graphical user interface (GUI). However, vi does have many of the tools and capabilities that we find in popular graphical text editors. The editor does take time and practice to learn and to use, but we believe that you will find the effort to be beneficial as the semester progresses, especially since vi is available on practically every existing UNIX-like operating system out-of-the-box.

To launch the vi text editor and open the existing round.c file, type vi round.c at the terminal command prompt. This tells vi to try to open the file named round.c, or to begin working on a new file with that name if it does not yet exist.

Once you hit the “Enter” key, a screen like the following is shown in your terminal.

The blue bar at the bottom is called the status line and tells us information about the file we are currently editing, including its name, the coordinates of the cursor in rows and columns, and the last modification time of the file. Specifically, [0001, 0001] indicates that our cursor is positioned on the first row of text, in column one.

The line of text directly below the status line, known as the vi command line, states there are a total of 226 characters of text in the file, spread across 13 lines.

Above the status line is the contents of the file. The light blue tildes (~) near the bottom indicate that there isn’t enough lines in the file to fill the whole terminal screen, so the last real line of the file is the closing brace (}) on a line by itself just after the return 0;.

The colors of various parts of the text inside the file is known as syntax highlighting. It’s not part of the file itself, but rather vi recognizing that this is a C source file and coloring the different parts as a visual aid for the programmer.

We will cover how to use vi in a later section. For now, hit the Escape key, then type :q! and hit the Enter key to exit vi and return to your terminal command prompt.

7.   Compiling your program

If you have programmed before, C might be slightly different from what you have previously experienced in that it is a compiled rather than interpreted language.

What this means for students both experienced and new to the C programming language scene is that your program must be compiled after each change you make to the source code. Compilation translates the human-readable source code into a binary “executable” file that the computer can then run as a program.

In this class we will use the GCC compiler, which can be accessed using the gcc command from the terminal command prompt.

To compile your program, type gcc round.c and hit the Enter key.

Here we see that the gcc command did not give any output. This is actually a good thing! It means that there weren’t any issues compiling your program. When we run the ls command again, there is now a new file:

This new file is named a.out, which is the default executable filename GCC uses if none is provided.

8.   Executing your new program

To run our newly-compiled program, type a.out and hit the Enter key. This command will execute the file named a.out in the current directory.

Notice that the terminal command prompt does not appear again. This is because the program is still executing - in fact, it’s waiting for you to enter a number.

The goal for this program is to output whatever numbers the user enters, but rounded to the nearest tenth. Type 1.06 and hit the Enter key.

The program returns the value 1.1 and returns us to the terminal command prompt, indicating the program has finished executing.

9.   Submitting an assignment

When you are ready to submit your assignment, you can click the “Submit” button at the upper right hand corner of the workbench. Vocareum will ask you if you are sure - click the blue “Yes” button.

As the submission is processed, a spinning icon will appear next to the “Submission report” button.

Once the submission is fully processed, this icon will disappear. You can then either click the “submission report” button to view the results of your submission attempt in a rich-text format, or run vi submit.rst to view a plain-text version.

Clicking the “submission report” button replaces the lab instructions with the following screen.

In this case, the submission was not successful because the computer could not find the file lb00.c. Note that this is short for “Lab #0” and thus starts with a lowercase “L”, not a digit one!

Let’s change the name of our round.c file to lb00.c so that we can make a successful submission. Run mv round.c lb00.c at the terminal command prompt to do this. If successful, no output will be generated. You can then run ls again to confirm that file has been renamed, or vi lb00.c to view the contents of the renamed file.

10.   Resubmitting an assignment

Once you are ready to submit again, just click the “Submit” button once more and confirm that you are ready to submit.

In order to verify that a submission is successful, you must view the submission report (either using the “submission report” button or using vi submit.rst) and look for Your submission has been recorded at the bottom.

The submission report will also be sent via email from cs159-wiki@purdue.edu to yourself and all members of your team, if applicable.

You can submit your assignment as many times as you like, up until the submission deadline.

• For lab assignments, this is 30 minutes before the next time your lab section meets.
• For homework assignments, this is 11 P.M. Eastern Time on Mondays.

Always make sure your program compiles first before submitting the assignment using the gcc command. Submissions that fail to compile will not be given credit.

We will next discuss how to fix the failing test cases and remove some of the deductions listed above.

11.   Interpreting submission reports

CS 15900 has an “auto-grader” that processes each student’s submission and assigns a preliminary grade which is based on the results of test cases run against your submission (output), the technique of your solution, and the formatting of the source code. The submission report gives you an idea of what you should expect the auto-grader will do when it presents your assignment to your lab instructor for final review.

The result of each test is either pass or fail, but you get partial credit depending on how much of the output from your program is considered “correct”.

In this example, we have failed all three test cases. Let’s look at the results for test #01 from the submission report. You can view these results yourself using the “submission report” button, or by running vi submit.rst. The snippets below are from the latter, but both sources contain the same information - just in different formats.

The first section shows us the test number, what the full command was to execute your program, and any input that was given. In this case, we see that the auto-grader passed the value 1.23 to the program:

==========
 Test #01
==========
:Command: ::

  | 'lb00.elf'

:Input: ::

  | 1.23

The next section shows us the status of the test. Here, the test failed because the output of your program did not exactly match the output of the solution program:

:Status: FAILED
:Error: program gave incorrect output

When a test case fails, the auto-grader will then include the output from your program, as well as the output from the solution program:

-------------
 Your output
-------------
::

| Enter measurement ->
| -=-=-=-=-=-=-=-=-=-
| The measurement is: 1.2

-----------------
 Expected output
-----------------
::

| Enter measurement ->
| -=-=-=-=-=-=-=-=-=-
| The measurement rounded: 1.2

If you look at these two outputs carefully, you should notice that the difference is that your program says “The measurement is:” while the solution says “The measurement rounded:” The Difference section visualizes this discrepancy in a text-based format:

------------
 Difference
------------
::

| Enter measurement ->
| -=-=-=-=-=-=-=-=-=-
| The measurement [-is:-]{+rounded:+} 1.2

Here, the auto-grader is telling you to delete is: and put rounded: in its place.

In general, anything between [- and -] should be removed, and anything between {+ and +} should be added.

After the final test case, if there are formatting problems or other issues with how you wrote your source file, the auto-grader will say Course standards violations detected:

======================================
 Course standards violations detected
======================================

------------------
 Format
------------------
:-0.75: Almost no comments present in the program
:-0.50: Missing program header block comment as the first item, line 1
:-0.10: Missing proper variable declaration comment, line 5

This says that if the submission were to be graded right now, you might lose 0.75 points for not including a sufficient number of comments in the program, 0.5 points for not including a program documentation header, and 0.1 points for specifically not putting a comment next to the float measurement; variable declaration on line 24.

12.   Making changes to your program using “vi”

In order to remove these preliminary deductions from our submission, we need to change our source code and resubmit. Run vi lb00.c again to open vi and edit the source file.

When you begin the vi text editor you will find yourself in normal mode. In this mode you are able to issue commands such as to copy and paste, save changes, find and replace, and make other edits.

Complete the following:

1. Type gg. This command will bring you to the first line of the file. You can also use your “up” arrow key until your cursor is on the first line.

2. Type :hlb (“:HLB”, but all lower case) and hit Enter. This will insert the course’s standard documentation header for lab programming assignments.

   Note

   For homework assignmens, use :hhw instead.

   Your source code file will now resemble the following:

   

3. Notice that the text that the :hlb command inserted is all blue. This is vi’s way of denoting text that is ignored by the computer, which is called a “comment”.

4. Next, move your cursor to the line for the lab number. You can do this by pressing k ten times, or press the “up” arrow key ten times.

5. Press l or the “right” arrow key eight times to move your cursor towards the end of the line.

6. Pressing the i key will start insert mode, which is how you type content into the file itself. This is indicated by -- INSERT -- appearing below the status line.

   

   You can now type freely and any text you enter will appear in the window as a new part of the file. You can also use your Backspace key to delete the character that is immediately to the left of your cursor.

7. Type space-zero-zero next to Lab #: so that it reads Lab #: 00.

   Note

   You may need to use your arrow keys to move your cursor so that you start typing AFTER the colon.

8. Use the arrow keys on your keyboard to move your cursor to the line that reads Program Description:.

9. Type a sentence or two describing the purpose of this program, such as "Rounds a user's measurement to the nearest tenth."

   Note

   To paste into the Vocareum terminal, right click anywhere inside the terminal window and select “paste”.

   Selecting text with your cursor will automatically copy it.

10. At this point, we have completed the program documentation header which will remove the 0.5 point deduction we had on our last submission.

11. Use your arrow keys to navigate to the line that reads float measurement;. To the end of this line (after the semicolon), type space followed by // user-provided measurement. This will remove the 0.1 point deduction.

12. Finally, use your arrow keys to navigate to the line that reads The measurement is and change is to rounded. This will fix our failing test cases.

13. Hit the Escape key to return to normal mode. Notice that -- INSERT -- is now gone from vi’s status line.

14. Note that there is now [+] located next to the ~/lb00.c filename in the status bar. This indicates that you have unsaved changes.

    At this point, the contents of your file should look roughly like the following:

    

15. Type :w and hit Enter to save your changes. The [+] indicator will disappear, and a message below the status line will show that the file was “written” (saved) successfully.

    Warning

    Your changes are not saved automatically, so you should periodically Escape and :w / Enter to save them as you work on your program. Failure to do so could result in the loss of your changes should your computer disconnect from Vocareum for any reason.

16. You can type :q and hit Enter to exit vi now.

    Note

    If you want to quickly save your changes and exit vi at the same time, you can combine :w and :q into :wq.

    If you want to exit without saving your changes, use :q! instead of :q. Note that this will not ask you to confirm, so be careful that this is what you want!

17. Try running gcc lb00.c to make sure your program compiles successfully. If no output is generated and the next line of text is your terminal command prompt again, you have succeeded.

18. Once successfully compiled, you can run a.out again to verify that our changing of is to rounded has taken place.

    

19. If you resubmit your assignment at this point, all of your test cases should now pass, and most of the deductions should now be gone.

13.   Viewing your grades and lab instructor feedback

In general, each homework assignment is worth 10 points (2 points for formatting, 4 points for technique, and 4 points for output) and each lab assignment is worth 5 points (1 point for formatting, 2 points for technique, and 2 points for output).

After the submission window for an assignment closes, the auto-grader will be run against the submissions from all students. These preliminary grades may be immediately visible inside Vocareum. Your lab instructor will then review all of the grades for your section for approval and make any changes if necessary. Once they are finished, you will receive an email that your grade has been finalized on Vocareum. Any grade that you see on Vocareum before you receive notification from your lab instructor that your grade has been finalized must be considered a preliminary score only and is subject to change.

The email from your lab instructor will contain a link to the guide on viewing programming assignment grades.

14.   Course policies regarding programming assignments

Purdue research indicates that automated resources such as ChatGPT produce code that is incorrect 52% of the time - worse than a fair coin flip.

It has become clear from previous semesters that these tools produce more harm than help to students enrolled in CS 15900. It is obvious to course staff when novice programmers submit code that utilizes concepts beyond what has been covered in the course - which is listed as prohibited on every assignment. As is the case with accessing any external source for assistance, if you are unable to create the work yourself, then it is unlikely that you are able to disguise it as your own.

When developing your programming assignment solution, please keep in mind that the utilization of any third-party programming assistance services, code repositories, or online integrated development environments (including but not limited to Chegg, CourseHero, Stack Overflow, GitHub, and Replit) is expressly prohibited.

All work on course programming assignments should be derived only from the course notes, the textbook, and any assistance obtained from current course staff members during office hours or via Ed. For homework assignments, this excludes assistance from anyone else (including but not limited to other students in the course, students who have taken the course previously, students who have never taken the course, former course staff members, roommates, romantic partners, family members, and tutors). YOU MUST COMPLETE YOUR OWN WORK!

It is our expectation that all work for CS 15900 programming assignments is completed within the Vocareum development environment provided to you. Submissions that provide little history of development within Vocareum may merit additional scrutiny from members of the course staff.

Our recommendations are the following:

• Start every assignment as early as possible. The earlier you start, the more opportunities you have to seek assistance from members of the course staff. This also affords you more time to carefully design and document your solution.
• Prior to each submission, ensure that your solution compiles using the gcc command. Submissions that fail to compile earn a score of zero.
• Submit early and often as you continue to make progress in completing your assignment. You may submit as many times as necessary until the submission deadline elapses. Each submission provides you with feedback for additional revisions. Only your latest submission is considered when determining correctness and adherence to the course programming and documentation standards.

15.   Completing the lab quiz

At the end of each lab session, your lab instructor will direct you to take your lab quiz. These quizzes are worth 5 points each and are based on the content of the written lab problems given in the lab assignment handout. Your lab instructor must proctor these quizzes - you may not take them on your own time.

Return to the “Week #1” content module on Brightspace, where you should find “Lab Quiz #0”.

The following restrictions are in effect for all lab quizzes, unless you have accommodations on file with the Disability Resource Center AND have discussed your accommodations with your LECTURER:

• You have only a single attempt to complete the quiz.
• You have 10 minutes to complete the quiz once you start it.
• Each question is presented one at a time.
• Once you move to the next question you cannot go back to previous questions.

Click the blue “Start Quiz!” button to begin the quiz once you are ready.

16.   Reviewing lab quiz answers

Lab quiz answers will be automatically released to all students at 3:30 PM on Fridays once all lab sections have finished taking the quiz.

1. Click “Course Tools” in the black Brightspace menu bar and select “Quizzes”.

2. Next, click the arrow icon next to the quiz name for which you want to review your answers. Click “Submissions”.

   

3. Click “Attempt 1”.

4. You can now see which questions you got correct, which questions you missed, and what the correct answers are for each question (indicated by a blue arrow).

   

17.   Creating teams

For information on how to create teams in Vocareum for your lab programming assignments, please review this document.