Deadline: Monday, June 29 (extended!!!)
Hello! Welcome to CS61C! We’re excited to have you on board :D
This lab may be a little long, but please read carefully; it will prepare you for the rest of the course!
Each lab will begin with a few objectives; use them to reflect on your learning and guide your thinking! Here are the objectives for this lab:
A quick clarification on some terms:
You can view the course policies on the policies page of the course
website. You are responsible for understanding and adhering to all
policies throughout the course of the semester. Please pay particular attention to the
Academic Dishonesty and Cheating sections.
We have modified our lab checkoff policy; please read New Lab Checkoff Policy on Piazza for details.
Unfortunately, assignments in this course do require some (sometimes boring) setup. Let’s get that out of the way.
CS 61C primarily uses a couple services, which are detailed below.
Unfortunately, some services and resources may be inaccessible or blocked in certain regions. As I’m writing this lab:
CalVisitorWiFi on campus).
If you’re unable to access any services or resources, please download and use the Berkeley campus
If the campus VPN is inaccessible or doesn’t work for you, contact us (Piazza, or email
cs61c [at] berkeley.edu) and we can try to work something out.
Most students should have a CalNet ID (and therefore, email ending in
@berkeley.eduemail if possible. This is your “Berkeley Google account” (or bConnected account, but nobody says that).
If you would like to use an existing account on a service, try to add your Berkeley email as a secondary email if possible.
Piazza is a discussion forum that we’ll be using as the main method of communication for this course. All announcements will be made here, and almost all questions or comments you may have should be posted here (unless we say otherwise).
We’ve already emailed invites to the 61C Piazza course to most students. If you’re not enrolled on our Piazza course, please refer to the policies section linked in the next paragraph.
Please read through the Discussion Forum section of our policies. Please remember and follow the Piazza Etiquette!
The “Hive” is a group of servers maintained by the EECS department. Campus is not very open right
now, but they live in Soda 330 if you ever want to give them a hug! You can intearct with these
servers remotely through SSH and the command line (more on that later). We’ve already installed most
of the software we’ll be using on the Hive machines, so you can work on most assignments on the Hive
if you want! You can find a list of Hive machines at Hivemind
(the names starting with
hive). Every Hive machine shares the same network mount, so files will be
synced across all the machines.
You will need to sign up for an EECS instructional
account, which you’ll use to access the Hive.
We’ll also be using your instructional account username as your primary ID for checkoff (though you
can use your
@berkeley.edu email address as a backup).
Note: If you can’t create an account for whatever reason, don’t worry! Fill out the form in the Non-standard Enrollment section, and continue without an account for now.
Gradescope is the platform we use for submitting and grading assignments. Programming assignments, homework, and quizzes will be submitted here. Exam results will also be returned here.
We’ve already invited most students to the 61C Gradescope course. To sign in, visit
Log In, then
School Credentials, then
Warning: Please ensure you set your
@berkeley.edu email as your primary email. If not, we
might not be able to find your Gradescope account, and you may receive an F in the class!
GitHub is a hosted Git service we use for code distribution, along with GitHub Classroom tools.
If you have an existing GitHub account, feel free to use that; repositories created in this course are private, and anything you do for this course shouldn’t affect the rest of your GitHub account.
If you don’t have a GitHub account or want to make a new one, sign up for a new account.
Most lectures and other video resources will be uploaded to YouTube. You will need to be signed into YouTube using your Berkeley Google account to view some videos. If you’re unable to view a video, make sure you’re using your Berkeley Google account.
We will be holding meetings (OH, lab checkoff, project parties, lectures, discussions, etc.) over
Zoom. When signing in, use the
Sign in with SSO option, enter
berkeley.zoom.us, and sign in with your CalNet ID.
Office Hours (OH), checkoffs, and project parties will be scheduled and managed through the OH Queue. Please use your Berkeley Google account when logging in; non-Berkeley Google accounts will not be able to use the OH Queue properly.
Please read the blue info box on the OH Queue page.
If you’re enrolled in the course as a Berkeley student, you can ignore this blurb.
If you’re a concurrent enrollment student, or otherwise not enrolled in CS 61C, please fill out this form so you can get access to our resources.
If you took CS61A and CS61B, you likely have some experience with a command line interface (CLI) and terminal commands, but we’d like to list some less common commands here that may come in handy during the course. For a review of the basic UNIX commands, look over this guide.. Be sure to read and understand section B of the guide as well as the commands below, since you’ll need them for Exercise 4.
Example commands will be formatted like:
$ echo "Hello world"
Typing that (without the
$) in your terminal will run the command. In this case, it just prints
As a CLI refresher, when typing commands or file paths:
<tab>will autocomplete the current term
<down arrow>will allow you to refill commands you’ve used previously without typing them again.
<ctrl> + awill move the cursor to the beginning of the current line (helpful for fixing mistakes)
<ctrl> + ewill move the cursor to the end of the current line (helpful for fixing mistakes)
<ctrl> + rwill let you search through your recently used commands
touch will create a blank file with the file name you provided.
$ touch example.txt
This will create a file named
example.txt with nothing inside.
If you’d like to create a file with contents already inside, you can use:
$ echo "Your contents here, inside double quotes" > example.txt
This will create a file with the name
example.txt in your current directory. If the file already
exists, it will be overwritten. The file will contain
Your contents here, inside double quotes but
without the double quotes. The
> symbol takes one argument which modifies where data printed to
stdout is piped. Here, we are redirecting them to a file named
You can also use the
echo command by itself, in which case it will print the string to the
terminal (without creating a file in the process).
$ echo "El Psy Kongroo"
You can view the contents of a file with the
$ cat example.txt
This will print out the file contents of
example.txt to your terminal. The file must be in your
current directory, but you can provide a relative or absolute path to print out non-local files.
man- Manual Pages
The manual pages (“man pages”) are great UNIX resources that are often underused; while not as versatile as Google, they contain documentation on UNIX components from program usage, language standards and conventions, and more. In this course we’d like you to get comfortable with them, especially for C and UNIX-related questions.
If you want the man page for a single program/command, you can run:
$ man command_name | less
The man page for a program typically contains information about what the program is used for, what
certain flags do when you invoke the program with them, and where to go for more information. Since
we piped the man page into
less, this page is scrollable (use your arrow keys or the space bar).
q to exit the man page and get back to your terminal prompt.
$ man echo | less
The above command should bring up the man page for the
If you want to search the man pages for a command that pertains to a keyword:
$ man -k single_keyword | less
This command will search the manual pages for a command with the keyword
how to open files in Vim? You can search for
editor and get a list of all editor-related commands
on your system.
ssh- “Secure Shell”
For this class, we’ll expect you to test most of your projects, homeworks, and labs on the Hive servers. To access the Hive servers remotely, you’ll be using the SSH protocol and programs.
Note: If you weren’t able to get an instructional account, you can come back here later!
You can find a list of Hive machines at Hivemind. There are
30 of them, named
hive30. Sometimes, a Hive machine may be down or
overloaded; when this happens, you can check Hivemind and find another machine to use.
Once you have an instructional account, you can SSH into an instructional server with the following command:
$ ssh [email protected]#.cs.berkeley.edu
Remember to replace
cs61c-??? with your instructional account username, and
hive# with a Hive
machine’s name. The default password is displayed by
WebAccount when creating the account, so you
might have to reset your password if you forgot it.
CalVisitoron campus, block SSH. Try another network (
eduroamif you’re on campus).
Connection refusedor other weird errors: the Hive machine you picked might be down. Try another one
Reserved for cs61c staff: try another Hive machine :)
When your connection succeeds, you should be able to interact with and run commands on your chosen Hive machine! To exit this SSH session, simply run:
Files on the Hive machines are stored on a network drive, so your account will have the same files on all 30 machines.
If you want to change your instructional account password, you can SSH into the update server:
$ ssh [email protected]
scp- “Secure Copy”
scp program is used for copying files between computers using the SSH protocol.
Sometimes, you may want to get individual files or entire folders from the Hive machines onto your
local system, or vice versa. You can do this by using
$ scp <source> <destination>
To specify a remote source or destination, use
[email protected]:path. To specify a local path, just
path. As an example:
$ scp [email protected]:~/some_folder/example.txt ~/Downloads/
Assuming my username is
cs61c-xyz, the above command would connect to
hive3 and copy
~/some_folder/example.txt on my instructional account to
~/Downloads/example.txt on my local
If I wanted to copy the other direction (from my local machine to a Hive machine) I would use:
$ scp ~/Downloads/example.txt [email protected]:~/some_folder/
Warning: you shouldn’t run
scp on the Hive machines (when you’re in a SSH session). Always run
it in a local terminal session!
scp by default only works with files. To copy folders, you need to tell scp to “recursively” copy
the folder and all its contents, which you can do with the
$ scp -r [email protected]:~/some_folder ~/Downloads/
vim is a text editor included on the Hive machines and many UNIX-based distributions.
Note: We’ll be using Vim in most of our examples and documentation, but we have no hard requirement on which text editor you use; you’re welcome to pick whatever you’re comfortable with, but you should know how to use at least one terminal-based text editor.
To open a file from your current directory, pass the file name to Vim:
$ vim filename
To open a file from another directory, use a relative or absolute path:
$ vim ../other_folder/filename
Some useful Vim commands:
||Closes (quits) Vim without saving|
||Closes Vim after saving|
||Saves your file|
||Force-quit Vim (for when you’ve made changes but do not wish to save them)|
||Insert mode, allows you to type into the file|
||Searches your file for the nearest occurrence of the string “cats”. Press
||Shows line numbers within your file|
Note: these commands are preceded by
<escape> because you’ll need to press the escape key on your
keyboard to switch you out of your current mode. For example, if I’m inserting (typing) into a file
and want to save, I’d have to hit
<escape> to get out of insert mode, then type
:w to save my
file. If you aren’t in a mode (i.e. you’ve just opened your file) you don’t need to hit escape
first, but it won’t hurt :)
If you want to learn more about Vim, one of our tutors, Yijie, wrote a great Vim for CS61C guide!
SSH into any Hive machine. Then:
check-register, and verify that your name, email, and student ID are correct. If anything is incorrect, run
This exercise will show you how to set up a Git repository (“repo”), use Vim, and work with a variety of Git commands. By the end of it, you should feel comfortable using SSH, editing files, pulling/committing/pushing, resolving merge conflicts. If you’d like to review your Git commands before beginning, you can check out this guide.
Make sure you’re logged into GitHub. Fill out the Lab Repository Registration
Form. Remember to read the form carefully, and follow the link
in the form to accept our invitation to the GitHub Classroom lab assignment. You may need to check
your email and confirm the invitation. If you don’t have an instructional account right now, enter
zzz in the form. You will be able to edit this later.
Before we start, let’s tell Git who you are. This information will be used to sign and log your commits. You may not need to do this if you’ve set up Git before, but if you’re on the Hive machines it’s likely a step you’ll need to take.
First, run the following commands on your local machine; make sure to change the name and email to match your information.
$ git config --global user.name "John Doe" $ git config --global user.email [email protected]
If you have an instructional account, SSH into a Hive machine, and run the same commands.
Git has the concept of “local” and “remote” repositories. A local repo is located wherever your terminal session is; if you’re in a SSH session, the local repo is a folder on a Hive machine; if your terminal session on your local machine, the local repo is located on your local machine’s filesystem. A remote repo (e.g. GitHub repo) is typically hosted on the Internet.
GitHub Classroom created a repository for you on GitHub, but not locally. To get a local copy of
this repository, you can use
git clone, which will create a local repository based on information
from a remote repo.
If you have an instructional account, SSH into a Hive machine. On the Hive clone the repository into
a folder called
$ git clone <link to repo created by GH Classroom> labs
If you don’t have an instructional account, that’s fine! Clone the repository into a folder called
labs_hive. For the rest of this exercise, any reference to your repository on the Hive is
referring to this repository.
$ git clone <link to repo created by GH Classroom> labs_hive
cd into this new folder. List all hidden files (
ls -a). Do you see a hidden file/folder?
There is indeed a folder called
.git. Its presence indicates that the current folder (folder
.git) holds a Git repository.
Take a look at your repo’s current remotes and status:
$ git remote -v $ git status
git clone has already worked a bit of magic here; there’s a remote called
origin, and its URL
points to your labs repo on GitHub! You’re on a local branch called
master, which is “tracking”
master branch on the
Throughout the semester, course staff may make updates to starter code to fix bugs or release new labs. To receive these updates, you’ll need to add another remote.
$ git remote add starter https://github.com/61c-teach/su20-lab-starter.git
If you ever want to pull updated starter code, you’d execute the following command:
$ git pull starter master
Since GitHub Classroom clones the starter repo when creating your repo, that command shouldn’t do anything right now.
Warning: please read carefully. Skipping a step may cause errors that will require you to redo the exercise.
The files for this exercise are located in the
lab00 folder in your lab repository.
first_set.txt. This file contains descriptions of UNIX commands. Use the man pages to figure
out which command they refer to; be sure to include any necessary flags. Once you’ve found them,
write the commands, one per line, in the provided
answers.txt should look similar to:
Save, add, and commit your changes with the commit message
"Answered first set". Push this
commit to your GitHub repo.
Now, we’ll need to copy the repository to your local computer.
exit. You should be back to your local terminal prompt.
scp -rthe entire
labsfolder from the Hive to your local machine. Remember why we need the
labs_hivefolder to a separate
Once you’ve copied the entire folder,
cd into this folder and open your answers file.
Above your previous answers, add commands (and relevant flags, if needed) that fit this second set of descriptions:
answers.txt should look similar to:
Save your changes, but do not commit or push them.
Go back to your repo on the Hive. Above your previous answers, add the command (and relevant flags, if needed) that fits this description:
answers.txt should look similar to:
Save, add, commit, and push these changes with the commit message
"Answered third set".
Go back to your repo on your local machine. Add, commit, and push your changes with the commit
"Answered second set".
You should get an error message from Git. What does this message mean? How do you resolve it?
After resolving the issue, you should have all your answers in
answers.txt on your local
answers.txt should match the following descriptions, with the numbers:
Commit and push your changes.
Still on your local machine, from the
lab00 directory, run:
This will add, commit, and push a log of your Git repo. If this succeeds, you should be able to
see a file called
git.log in your GitHub repo.
Last bit of reading for this lab, I promise.
To submit your work, push your work to your lab repository on GitHub.
Many of the labs will have an autograder portion. If a lab has an autograder portion, it will
specify this in the
Checklist section at the bottom of the page. To submit to the autograder,
you’ll need to push your work to your lab repository on GitHub. Then go to the
assignment on Gradescope, and submit your lab repository. After a short wait, the page should show
your autograder score for the current lab (and previous labs). Make sure you passed the autograder
Each labs will require you to complete a checkoff to receieve credit.
You will be required to
work on labs in pairs, and both partners are required to be present during checkoff. This helps
us reduce the time we spend on checkoff and allocate that time towards helping students and
developing course materials. It also helps you by giving you someone to discuss class material with
and work together with to solve lab problems.
If you have not done so already, please read through the Labs section of our policies.
We have modified our lab checkoff policy; please read [Important] New Lab Checkoff Policy on Piazza for details.
Before your scheduled checkoff, please make sure that:
Lab Autograderassignment on Gradescope. Your work should pass the autograder tests, and you should have this page open for checkoff.
cs61c-???, the one you use to log into Hive machines).
We will be using an appointment-based system on the OH Queue to schedule checkoffs. Checkoff slots for the week will be released on Sunday around 9PM PDT. You (and a partner) may then sign up for a 13 minute checkoff slot. If you have a partner, you both must sign up for the same slot (sometimes there are multiple slots at the same time, watch out!). You must have completed the requirements before your checkoff slot starts.
To sign up for a checkoff slot:
Add yourself to the section. Fill out the resulting form (Assignment:
Lab ##, Question:
Partner: <PARTNER_NAME>) and submit it. If you have a partner, you both must sign up for the same appointment (try to sign up at the same time). If you don’t have a partner, you may be paired with someone else without one. You may not sign up for more than one appointment across Tuesday+Wednesday, and one appointment across Thursday+Friday.
Upcoming Appointmentson the home page. When the TA is ready, a green
Join Callbutton will appear. Click it to be taken to the Zoom call.
You will receive credit for a lab after completing a checkoff with a TA/AI. You can (and should)
verify this by looking at the
Lab## Checkoff assignment on Gradescope, replacing
## with the
lab number, and making sure it is
Submitted. It is your responsibility to verify that this
happens for each lab; we will not be retroactively giving credit for checkoff.
If you completed checkoff in the correct timeslot, but Gradescope displays a
Submitted ???? late message, you can ignore this message for now; we’ll update this after the lab
deadline has passed.
You made it! That was quite a bit of reading and head-scratching, but you’re now somewhat more familiar with the tools you’ll be using for the rest of the semester. Worth it!
This lab has an autograder. After you’ve pushed your work, submit your GitHub lab repo to the
Lab Autograder assignment on Gradescope. Make sure the autograder passes!
Please check that you and your partner have:
Lab Autograderfor this lab
After a TA/AI has checked you off, please make sure that the corresponding lab assignment on
Lab## Checkoff) is marked as
These are some tools you may find helpful, but are by no means required for this course :)
CS61C doesn’t endorse any particular text editor or IDE. Many people get by in this course using a text editor with no frills (think: Vim/Emacs/Nano). We’ll expect you to know how to use at least one terminal-based text editor (again, Vim/Emacs/Nano), since you’ll be dealing with the command line a lot.
For your own work, you may find it nice to have CLion from JetBrains if you’re used to working in IntelliJ from CS61B. Note though that we won’t be providing any course-official support, so setting it up and maintaining it are up to you.
The majority of students do their work in a local editor (Sublime, Atom, VSCode) and use Git to copy their files from their local machine to the Hive. Some students also set up Cyberduck to make copying files over easier. Again, we won’t provide any course-official support, but you’re welcome to do what works best for you.
Tired of typing up an entire SSH command and password? Follow the instructions on
this Piazza post (
"Useful additional setup information for labs and