ABC0 documentation

Join the Discord, the invite can be found towards the top of the syllabus located here. You may create a new account or join with an existing one. Once you've joined, introduce yourself with your name, and what classes you're taking so that appropriate roles can be assigned, granting you access to the class channels.

Instructions on how to log into Lab46 via shell can be found here.

After you've logged into lab46 via shell, we'll be using Mercurial to clone a remote repository.

You can accomplish this by running fixrepo at the lab46 prompt:

lab46:~$ fixrepo

and follow and instructions, respond to any actions requested.

Should you wish to do things more manually, do the following:

This is done with the command:

 hg clone ssh://cgaffne1@lab46.g7n.org//var/repos/hg/user/cgaffne1 ~/src 

Where uppercase USER is replaced with your lab46 username, and lowercase user remains unchanged.

This will clone the repository into a directory named src that is a subdirectory of your home (~) directory.

We will also be cloning a second repository for the semester, done with the command:

 hg clone ssh://cgaffne1@lab46.g7n.org//var/repos/hg/user/cgaffne1/fall2023 ~/src/fall2023

Where SEMESTER is your semester written as the name of the month in lowercase and then the year in YYYY format, without spaces, e.g. fall2023.

At the top right of any lab46.g7n.org page should be a button to log in, shown here:

The username and password should be the same as the username and password you used to log into Lab46 via shell in previous steps.

Your personal development system will be the Raspberry Pi 4, a link to which will be in the class syllabus, in the “Referenced Books” section. Instructions on how to set up should be included in the purchased kit.

The steps here are very similar to the steps in the section “Clone lab46 semester repo on lab46”; however, assuming your development system has just been set up with Raspberry Pi OS, then Mercurial is not yet installed. Luckily, this is easy on most UNIX-like operating systems. Simply open your terminal, which should be located at the top of the desktop, and type hg. Once you enter that command, you should be prompted to install Mercurial. Once Mercurial is installed, you may proceed. You should start by creating a directory anywhere you'd like, using the mkdir command, i.e.

 mkdir NAME 

Where NAME is the name you'd like to give the directory. do not freak out when the terminal spits back nothing. the directory is created, and you should be able to see it by typing “ls”.

After making this organizational directory, we will now clone the repo. To do so, we'll use Mercurial's hg clone command again, into a new src directory under our directory, like so:

hg clone ssh://cgaffne1@lab46.g7n.org//var/repos/hg/user/cgaffne1 /NAME/src 

Where NAME is the name you gave the directory, and you are currently in its parent directory.

Once that is done, we'll clone the semester repo:

hg clone ssh://cgaffne1@lab46.g7n.org//var/repos/hg/user/cgaffne1/SEMESTER /NAME/src/SEMESTER

Recall that SEMESTER is the lowercase name of the month and the year in YYYY format, without spaces. e.g. fall2023

Let's enter the SEMESTER directory using cd, as such:

cd /NAME/src/SEMESTER

From here we'll create a class directory with the name of the class, e.g. c4eng, and a subdirectory of it for our project abc0:

mkdir -p c4eng/abc0

This is where we'll put our project files coming up in the next steps.

Assuming we are currently in the SEMESTER directory, we can enter the abc0 project directory using

cd c4eng/abc0

To create and edit info.text, we can use the nano text editor via the terminal:

nano info.text

This creates the file info.text and starts editing it. You can see all the commands at the bottom of the terminal, with ^ signifying that you must hold the CTRL key while pressing the respective letter. Now you can populate info.text with some information such as your preferred name, your program (e.g. Engineering Science), your preferred contact email, discord username, and any additional information you may want to supply to the professor.

When you are finished editing the file, use the “Write Out” command and chose a format. Press enter to send the command. Then “Exit” the file. Note, the ^ symbol correspond to the CRTL key and the M corresponds to the ALT key.

If you wish to view this information, you can use the cat command:

cat info.text

This displays the content of the file on the terminal. It is most useful when you wish to view text files.

Assuming we are still inside abc0, the next steps are writing a “Hello World” program in C, compiling, and then executing it. A “Hello World” program is a beginner program that demonstrates how to structure our code, invoke our code, and print some output, namely “Hello World”, to the terminal. Let's start editing hello.c by typing

nano hello.c

Now that we have a file named hello.c and we are now editing it, we can write the following code:

#include <stdio.h> 

int main(void)
{
	printf("Hello World\n"); 
	return 0; 
}

Later we'll go into more depth on what the surrounding lines of code do, but for now we should know that printf(“”); prints text within the quotes to the screen.

Now we want to compile this code into instructions that the computer can understand. We can do that simply using the GCC compiler:

gcc hello.c -Wall -std=gnu18 -o hello

This will give us our executable as a file named hello, which we can now run by typing

./hello

If everything has worked correctly, you should see “Hello World” printed to the terminal.