Due: next Monday before 2359

Part 0: Lab Ground Rules

• Plan to have multiple conversations with your instructor and with your classmates throughout the lab time, discussing how to write, debug, format, and understand great code.
• Deadline: Sometimes you might finish the assignment during the lab time itself, and other times you will have to finish outside of the lab time. The completed lab is generally due to be submitted electronically by Monday night after the Thursday lab.
• Collaboration Policy: Labs follow the same rules as homework: You can receive help from your instructors, MGSP, or classmates, but must document (in code comments usually) what help you have received. And you can never copy code; you must do the actual typing-up of your own programs, without copying from someone else's solution directly.

Part 1: The Computing Environment in Your Laptop

The system setup page and resources page are your starting points for help on how to use the computing environment and get things done for this class.

Of course, you should have already followed these instructions to set up your Ubuntu environment on your laptop. If not, now is the time to do it!

The computers in the lab are also running Ubuntu! To get them set up with your ic210 directory, and the submit script that will be used to submit your labs, just like in WSL, follow these instructions. To open a terminal on an Ubuntu machine (like the ones in the lab), you can click Ctrl+Alt+t.

Part 2: Editor

Choose your editor

• atom - a new-ish text editor that's easy on the eyes and the brain, but hard on your computer's RAM (written in javascript) ← nice if you want something Windows-based
• vi/vim/gvim - lightweight and powerful text editor, based on never having to use a mouse again. Requires a bit of learning the key commands ← Dr. Crainiceanu's favorite choice!
• emacs - Feature-rich text editor, which is more or less infinitely customizable. ←many other CS professors like this one best!
• geany - Similar features to Atom, but runs on Linux and is much faster to start up ← well-liked by some, unknown to others

The way you open these text editors is a bit different: For Atom (which runs both on Windows and Linux), you open Atom from your start menu, then you navigate to your ic210 folder to create and edit files.

If you're using gvim, emacs, or geany you can open your text editor by running a command in the terminal directly. This can be pretty convenient, since you already have to have a terminal window open to compile and run your programs.

For example, to open or create a file hello.cpp using geany, assuming you are already in the ~/ic210/lab01 folder, you could just type:

geany hello.cpp &

Part 3: Your First Program

1. Open a Linux (Ubuntu) terminal window. In WSL, this means opening the Windows Terminal (be sure your tab has the penguin!) or, if you couldn't get that installed, running wsl from the start bar. In Ubuntu labs, that means clicking Ctrl+Alt+t, or selecting Terminal from the menu.
2. You should see a prompt like

   m012345@WK2ESUIO4MID:~$

   This is actually telling you some useful information! In this example:

   • m012345 is your username (should be the same as your USNA username)
   • WK2ESUIO4MID is the name of your computer (sorry, ITSD doesn’t like to give a nice looking name to your laptops)
   • The ~ is the current directory. A tilde ~ indicates your home directory, which is the base of where all your personal files will be stored in Linux.

3. Type

   ls

   to see the contents of your current directory. You should see something like

   Desktop Downloads bin ic210

   The Desktop and Downloads are links to those folders in Windows, and ic210 is a link to the exact same folder called ic210 on your Desktop.

4. Of course the ic210 directory is the place to be! To move into that directory type

   cd ic210

   Notice that your prompt changes to indicate you are now in a different directory!

5. It's a good idea to always start and end any period of work that you do, by syncing up with git. More detail on this below, but for now you just need to run:

   210sync

6. Now we want to make a new directory to hold your files for lab01 using "mkdir" command, and finally change to this new directory:

   mkdir lab01 
   cd lab01
   

7. Open your preferred text editor.
   • For Atom (which runs on Windows):
     1. Open Atom from your start menu
     2. In Atom, navigate to your lab01 folder that is under ic210, and create (and save) a file called main.cpp.
   • If you use vi, in your terminal:

     gvim main.cpp& 

     (Try and learn a bit about Vim: Vim cheatsheet, the interactive Vim tutorial, Vim Introduction and Tutorial)
   • If you use emacs,

     emacs main.cpp & 

     (Try and learn a bit about emacs: Emacs Essentials, a bigger list of commands, a much bigger list of commands)
8. Now use your text editor to copy in the following source code into the main.cpp file:

   #include <iostream>
   
   int main()
   {
     std::cout << "Hello World!" << std::endl;
     return 0;
   }
   

   When finished, save your file.

9. Compile (and link)

   If you want the programs you write to actually do something then you must compile them (turn source code into machine language). Converting high-level C++ source code into machine language is very complex, but compiler vendors solve this problem for you.

   To compile your program,

   • Make sure that you have a terminal open from before.
   • In the terminal, the current directory is where you saved main.cpp.
   • Once you are there, compile by typing into the terminal

     g++ main.cpp -o m012345

     (Of course, use your alpha instead of m012345.)

   There should be a new file in your working directory called m012345. Check this by typing:

   ls

   If you omit the "-o m012345", which we will often do, then a file with default name of "a.out" is created. Try:

   g++ main.cpp
   ls 

   The new files m012345 and a.out are the "executable file" for your program.

   If you do see any error messages from g++, then get assistance from the instructor. Tips for deciphering error messages are given below at the end of this tutorial.

   Note: technically, the single command you issued actually "compiled" and "linked" your program. We'll talk much later about this, but in short "linking" (amongst other things) takes your code and combines it with other code provided elsewhere to do standard things like input and output (this is referenced by the #include <iostream> line in your code). Often, we'll informally call this whole process "compiling."

10. Run!

    Once you successfully compiled and linked your program (no errors), then you are ready to execute your program. In your current working directory, you will see a new file called m012345 (or whatever you have named it). That is your program. To execute a file, type the file's name preceded by a "dot slash" (literally, "./") and hit the enter key.

    
    Note: the "dot slash" is telling the computer to look for the program (m012345) in the current directory (indicated by the "dot").
11. Program Output:

    Your program will output to the same terminal from where it was executed, as seen above.

    Now, let's view the executable file you just executed. Type

    ls -l

    to list details of the contents of your current working directory.
    • There is a file named main.cpp – it is your source code file. Note the size of the file (95 byes in our example).
    • The file called m012345 is your program's executable file, which is combined with all of the other necessary machine code to run your program. Note the size (7782 bytes in our example)!! The increase in size is due to the code that was “included” or linked into your program.
    

Part 4: Let's do it all over again!

Repeat Part 3 of this lab all over again, with these changes:

1. First, close all open windows (including the editor and terminal).
2. Open a terminal and "cd" to the correct directory for lab01.
3. Instead of entering the "Hello World" program, enter in this simple addition program (name your source file add.cpp instead of main.cpp and make sure you replace first line comment with your actual name and alpha):

   add.cpp	sample run
   // (Your name and alpha) // This program adds two numbers #include <iostream> int main() { int number1, number2, sum; number1 = 12; number2 = 13; sum = number1 + number2; std::cout << "The sum of these two integers is " << sum << std::endl; return 0; }	~/$ ./add The sum of these two integers is 25

4. Compile your program giving the executable the name add.
   • Now, what do you need to change when you compile your program?
   • See Part 5 below, if you have errors in compilation.
5. Run your program, making sure it prints out the right answer! Fix it if it doesn't!

Part 5: Fixing errors in compilation

How to read the error message

• Each error message includes a number, which represents the line number of the error. Go to that line number to see where the problem is.
• Every syntax error must be corrected before a program will compile. Sometimes it is clear what's wrong, and other times you may have a hard time figuring out how to correct a syntax error.

Tips

• Save program files before compiling
• If an error is flagged on a line that looks perfectly fine, sometimes it is the preceding line that is messed up. Check it too!
• Check for missing or extra ; and } characters
• Compile your program in small chunks. Don't wait to compile your code until you complete the entire program.
  • When you write some chunk, try compile it and fix errors for the chunk.
  • If you fix all the errors for that chunk, then add some more chunks.
  This way you can focus on errors in a small section of code. Waiting to compile until the entire program is completed can lead to large numbers of errors.
• Messages that say "Cannot convert from ... to ..." usually mean you are trying to assign the wrong type to a variable.
• Check your typos. A common mistake is to name a variable one thing but spell it wrong or use some other name later.
• Sometimes, one simple problem can cause the compiler to find tons of errors (like forgetting to include using namespace std;. Correcting that one line can make all of those errors go away!
  If you compile and see an unusually large number of errors don't panic. Often a simple change will correct them.
• If you can't figure out what's wrong - ASK!!!

Errors on purpose: Don't skip this part!

• remove a semi-colon.
• change a "<<" to a ">>".
• change the variable number1 to Number1.
• remove the ending }.
• remove the "#include <iostream>" line.
• change the "std" from "std::cout"

Part 6: Write code to submit

1. In your Terminal, cd to ~/ic210/lab01.
2. Create lab01.cpp with the following content:

   #include <iostream>
   
   int main()
   {
      std::cout << "Hello World!" << std::endl;
      std::cout << "This is a 1!" << std::endl;
   
      return 0;
   }
   

3. Modify the program lab01.cpp so that it's output matches what's shown exactly!
   

   required output Hello World! Hello Solar System! Hello Galaxy! Hello Universe! Hello ... ? This is a 1! This is a 2! This is a 3! This is a 4! This is a 5!

   Use editor commands: Your focus is on using the editor to make these changes as efficiently as possible! In other words, of course you can do it, I want you to concentrate on doing it smart! It's almost a puzzle to use as few keystrokes as possible. In particular, what editor commands would do the following? Copy a line Paste Delete (or replace) a word

Submit this lab01.cpp to the submission system

1. Make sure your are in the directory that contains the lab01.cpp file.

   cd ~/ic210/lab01

2. Submit your program by giving the following command:

   ~/bin/submit -c=IC210 -p=lab01 lab01.cpp

3. Important: Using your web browser, check the submission server and see if your work passes the test case.

   If you did not get the output 100% correct, the page should give you an indication of what's wrong with your output.

   Keep fixing your program and resubmitting until it works perfectly.

Part 7: Syncing your code to git

You'll be writing a lot of code this semester. It would be a shame if anything happened to it!

Run 210sync to save your work in github.

Remember to run 210sync every time you do some work, either on your laptop or on your lab machine. Also make sure you always do your work in your ic210 directory!!