Shall we have you write your first program?
At this point you should have all of your module and pset folders created. If not, please refer to the File Management Resource in Helpful Resources.
In the terminal window, navigate to the ~/workspace/module1/exercises folder
If you are not sure where you are located, use the command pwd to list the directory you are at and if you are not in the ~/workspace/module1/exercises folder use the command cd then hit enter, and type the command cd ~/workspace/module1/exercises to change directories.)
$ pwd
/home/ubuntu/workspace/ (You will see something similar to this)
$ cd ~/workspace/module1/exercises
(Incidentally, ~ is the name of your system's "home" directory)
Now create a new folder called hello, and cd into this directory.
$ mkdir hello
$ cd hello
You should now be inside of the ~/workspace/module1/exercises/hello folder, where you will make a new file named hello.c. The linux command to create a file is touch. Then verify that the file was created by using the command ls to list the contents of the current folder.
$ touch hello.c
$ ls
hello.c
You can now look at your directory on the upper left side of the CS50 IDE and click the dropdown arrow next to the folders module1, exercises and then hello, to see the new file you just created. You can double click the hello.c file to start writing your program! (You will see a new tab with the name hello.c above the terminal window. This is where you will write your program)
First, checkout this quick video, where Zamyla explains the steps as she writes the program. (We skipped ahead past the intro where she talks about getting set up, because our setup process is a little different).
Proceed to write your first program by typing precisely these lines into the file:
#include <stdio.h>
int main(void)
{
printf("hello, world\n");
}Notice how CS50 IDE adds "syntax highlighting" (i.e., color) as you type. Those colors aren’t actually saved inside of the file itself; they’re just added by CS50 IDE to make certain syntax stand out. Had you not saved the file as hello.c from the start, CS50 IDE wouldn’t know (per the filename’s extension) that you’re writing C code, in which case those colors would be absent.
Do be sure that you type in this program just right, else you’re about to experience your first bug! In particular, capitalization matters, so don’t accidentally capitalize words (unless they’re between those two quotes). And don’t overlook that one semicolon. C, like most programming languages, is quite nitpicky!
When done typing, select File > Save (or hit command- or control-s), but don’t quit. Recall that the leading asterisk in the tab’s name should then disappear, indicating that the file has been saved. Click anywhere in the terminal window beneath your code, and be sure that you’re inside of ~/workspace/module1/exercises/hello (Remember how? If not, type cd and then Enter, followed by cd workspace/module1/exercises/hello and then Enter.) Your prompt should be:
username@ide50:~/workspace/module1/exercises/hello $
Let’s confirm that hello.c is indeed where it should be. Type ls
followed by Enter, and you should see hello.c.
$ ls
hello.c
If not, no worries; you probably just missed a small step. Best to restart these past several steps or ask for help!
Assuming you indeed see hello.c, let’s try to compile! Cross your fingers and then type
$ make hello
at the prompt, followed by Enter. (Well, maybe don’t cross your fingers whilst typing.) To be clear, type only hello here, not hello.c. If all that you see is another, identical prompt, that means it worked! Your source code has been translated to object code (0s and 1s) that you can now execute. Type
$ ./hello
at your prompt, followed by Enter, and you should see the below:
hello, world
And if you type ls followed by Enter, you should see a new file, hello, alongside hello.c. The first of those files, hello, should have an asterisk after its name that, in this context, means it’s "executable," a program that you can execute (i.e., run).
$ ls
hello* hello.c
If, though, upon running make, you instead see some error(s), it’s time to debug! (If the terminal window’s too small to see everything, click and drag its top border upward to increase its height.) If you see an error like expected declaration or something no less mysterious, odds are you made a syntax error (i.e., typo) by omitting some character or adding something in the wrong place. Scour your code for any differences vis-à-vis the template above. It’s easy to miss the slightest of things when learning to program, so do compare your code against ours character by character; odds are the mistake(s) will jump out! Anytime you make changes to your own code, just remember to re-save via File > Save (or command- or control-s), then re-click inside of the terminal window, and then re-type
$ make hello
at your prompt, followed by Enter. (Just be sure that you are inside of ~/workspace/module1/exercises/hello within your terminal window, as your prompt will confirm or deny.) If you see no more errors, try running your program by typing
$ ./hello
at your prompt, followed by Enter! Hopefully you now see whatever you told printf to print?
If not, reach out for help! Incidentally, if you find the terminal window too small for your tastes, know that you can open one in a bigger tab by clicking the circled plus (+) icon to the right of your hello.c tab.
You’ve begun to program!
Incidentally, you've also (unknowingly) just completed a portion of Pset 1! Namely, you did the section called Hello C.
Let's copy this work into your /pset1 directory, so you don't have to redo it later when you are working on the rest of the problem set. In your terminal, type
$ cp -r ~/workspace/module1/exercises/hello ~/workspace/pset1/hello
Then verify that this worked correctly by typing
$ ls ~/workspace/pset1
hello/
You should see there is now a hello/ directory inside pset1/.