Generally, you will have access to an operating system, which will both organize information and present it in a user friendly manner. However, there are instances, especially in this class, that will require the use of the terminal. The terminal, also known as the command prompt on windows, serves as the main connection between you and the computer. It allows you to navigate files and folders, run programs or scripts, remote into other systems or connections, and a whole variety of things. Opening the terminal is different on every OS, but is generally similar.
WINDOWS OS– Press WINDOWS+R, this will open up the run prompt, then type “CMD”. The command prompt should be open
LINUX/PIOS– Navigate to APPLICATIONS, then click and run the TERMINAL application
With the terminal view open, we now have access to an array of commands, these commands, with examples, are as follows:

cd - used to navigate into a directory (folder) or sub directory. cd .. can be used to exit the directory
cd src/fall2023 will go into the src directory and then into the fall2023 subdirectory within it
ls (dir on windows) - used to see the subdirectories and files or programs in the directory you are currently in.


cat - looks into a directory or file
mkdir - makes a directory
nano - creates a text file with name mentioned, or edits text file
rm - removes a directory or file
./ - runs a program
sudo - runs the following command with admin permissions
gcc - compiles a C program
ssh - allows for remote connection to a server, or another device
hg - prefix for all repository commands, which include:

• hg add - adds files in directory to repository
• hg commit - commits the added files to the repository with a message for why they are there
• hg push - pushes commited files to the repository to be added to another system
• hg pull - pulls the files pushed into the repository
• hg update - updates the systems current repository to match the one pulled

In this section, we will be going over the basics of writing, troubleshooting, and compiling C code, aswell as basic functions and basic programs that are either useful, or a good refresher.

C code has a structure that should typically be followed, if you want a program to be compiled. Since the computer reads code in the same order we do, generally code is structured like this:

libraries
variables and definitions
int main
return
function definitons 

LIBRARIES
Libraries function as a way for the computer to get definition of functions not already embedded in the kernel / language. While not necessary, as you can create custom functions within your own code, they are useful and prevent you from having to create your own functions and operations. To include a library, you write #include.
MAKE SURE YOU HAVE THE LIBRARY INSTALLED

To begin, a text file will be needed. We can either create it in the terminal using the NANO command, or we can use a text editor to write the code instead. In this section, however, we will assume you are using the terminal. The file extension should be .c to decern that it is indeed C code.

 nano program.c 

We now should be within the GNU text editor. We can now write our code. For this example, we are going to be writing a basic hello world script. However, there will be a list of other basic functions, aswell as a list of definitions, and more wiring pi orientated code in section 4.
The first lines with our code should be our libraries. Libraries allow the computer to look into another file for definitions of certain functions not built into the kernel or into the language. For example, to control a servo, you would use the servo.h library, or you could create all the functions and calculations yourself.
to include a library, use the #INCLUDE line. Within GNU, the text will turn a different color, then write the name of the library used. In this example, we need the stdio.h library, thus we need to write,

 #include stdio.h 

This is the only library we are going to need for this program, so we move on to declaring variables.
in this example, no variables are needed, so we can skip writing and defining our variables.
Now, we need to start our main line, to do this, we simply use

 int main(void){ 

within this block will be all of our code, now we write our print function, for this we use

 printf("hello world!\n"); 

\n ends a line, and printf allows for text or data to be printed to the terminal
finally we can end the code with our return and closing bracket

}

now we can close the gnu program by doing ctrl+x and then saving changes and naming the file. Before we can run the program, it needs to be compiled.
To compile, we use the gcc command in the terminal

 gcc program.c -o program 

if we used extra libraries, such as wiringPi in the future, we will add -lwiringPi or -l(library name) before the -o.
if there are any errors in your code, the compiler will fail and give you the errors it found, if not, then
You can run the program using ./program
CONGRATULATIONS, YOU HAVE WROTE YOUR FIRST BASIC C PROGRAM