Part 0: Lab Ground Rules

Read the instructions carefully. Read every word.

Part 1: The Computing Environment

Login: Ubuntu

Your Unix Account

Part 2: Editor and project

Choose your editor

We will be using the Unix environment to create, compile&link and execute C++ programs. First, you must choose a text editor to create your first C++ program. Sounds easy, right? Wrong! Your choice of text editor will mark you for life. Choose wisely!
Real Programmers

Part 3: Step-by-step instructions to creating the "HELLO WORLD" program

  1. Directory setup.

  2. Edit the source code

    Explore vim Explore emacs
    Try and learn a bit about Vim using the below references: Try and learn a bit about emacs using the below references:

    Open your preferred text editor. For example, if you use vi, in your terminal window type

    vi main.cpp 
    or if you use emacs,
    emacs main.cpp & 

    Now use your text editor to copy in the following source code into the main.cpp file:

    #include <iostream>
    using namespace std;
    
    int main()
    {
      cout << "Hello World!" << endl;
      return 0;
    }
    
    When finished, save your file.

  3. 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, first make sure that you have a terminal open from before, whose current directory is where you saved main.cpp. Once you are there, compile by typing into the terminal

    g++ main.cpp -o m012345
    There should be a new file in your working directory called m012345. (Use your alpha instead of 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 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."

  4. 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.

    screenshot
    Note: the "dot slash" is telling the computer to look for the program (m012345) in the current directory (indicated by the "dot"). In some cases you can get away with not including this, because your computer is set up to automatically look for commands in the current directory (amongst other places), but including the "dot slash" is safer because it will always work.

  5. 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.

    screenshot

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

You just accomplished quite a bit; you typed in a C++ program, compiled it and executed it. It is important that you understand all the steps involved, and that you are comfortable using a text editor and the terminal.

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

add.cppsample run
// (Your name and alpha)
// This program adds two numbers

#include <iostream>
using namespace std;

int main()
{
  int number1, number2, sum;
  number1 = 12;
  number2 = 13;
  sum = number1 + number2;
  cout << "The sum of these two integers is "
            << sum << endl;
  return 0;
}
~/$ ./add
The sum of these two integers is 25

Compile your program giving the executable the name add, and run it, 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

When you make certain kinds of common mistakes (syntax errors), the compiler won't be able to understand your program and will issue error statements in the terminal window.

Tips

You will improve as you see enough errors to associate the messages with the syntax error. Here are a few simple tips:

Errors on purpose: Don't skip this part!

Experience and practice help a lot here. So for each of the below, purposefully make the syntax error in your current program and try to compile to see what the error message is. Correct the error before introducing the next error into your program (e.g., only add ONE ERROR at a time). Go slowly and pay attention, this will save you time later!

Part 6: Using Your Laptop

You're going to be writing and running a lot of programs this semester. Therefore, the following questions are important: We'll take some time in class to address these questions.
  1. Where to work. You will be writing and running your programs You will probably want to bounce back and forth - work on something in the lab, continue work on your laptop VM later.
  2. Where to store your work. You have three basic places to store files.
    1. Your laptop's filesystem (i.e., Windows).
      Storing stuff on your laptop's Windows filesystem is not a very convenient option because the writing, compiling and running will be happening either on the CS Department Unix lab machines or on your VM. Anything on your laptop's Windows filesystem would have to be constantly copied back and forth.
    2. Your VM's filesystem.
      Storing stuff on your VM's filesystem is nice in some ways - you can work regardless of whether or not you have network access, for example. On the other hand, it's got some serious negatives. If your laptop dies you lose all your work. If the file on your laptop that contains the VM's state gets corrupted, you lose all your work. Finally, the work you do in the lab is not available on your VM and vice versa, unless you go back to constantly copying files back and forth.
    3. Our recommendation: your CS Department home directory.
      It turns out that storing stuff in your CS Department home directory is the best option.
      • The lab machines use this storage; when you log in with a lab machine, you will see your files.
      • It's also accessible from your VM, as long as you have a network connection, thanks to the "csunixmount" script that's preloaded on your VMs.
      Use the csunixmount script and keep everything in your CS Department home directory.

csunixmount, csunixunmount (in VM)

Bring out your laptop, pull up VM, and then pull up a terminal.
  1. In your VM terminal, give the command:
     ls 
    Note the directory "csunix". Give the command
    cd csunix
    then
    ls
    Note that it's empty. Give the following command to go back to your home directory
    cd ..
  2. Run
    csunixmount
    Now cd to csunix again
    cd csunix
    and do an ls:
    ls
    You will see the files you worked on in your the lab machine.
  3. Give the command:
     cd ~ 
    Note ~ means your home directory in VM. Give the command
    csunixunmount
    and do
    ls csunix
    Now it's empty again. Give the commands:
    csunixmount
    ls csunix
    Files are back!
csunixunmount before pausing your VM

If you "pause" your VM before exiting VMPlayer (as opposed to shutting the VM down), we recommend you run the csunixunmount script first.

Passwordless mounting (in VM)

When you run csunixmount it asks you for your network password because you are connecting to a USNA server. We can skip the password requirement by using public/private keys (remember SY110?). You generate a key pair in your VM, keep the private key in the VM, and send the public key to the USNA server. Once you do this, future ssh or csunixmount will not prompt for a password.


   cd ~
   ssh-keygen -t rsa
   

When asked where to save the keys, just hit ENTER to accept the default location. When asked for a password, just hit ENTER twice to skip that requirement.

You now have a key pair in your ~/.ssh folder. Let's copy it to the lab machines:


      scp .ssh/id_rsa.pub csmidn:
   

And now we login to the lab server ourselves for final setup:


      ssh csmidn
   

Copy the public key to the authorized keys file:


      mkdir -p .ssh
      touch .ssh/authorized_keys
      cat id_rsa.pub >> .ssh/authorized_keys
      exit
   

Done! Now you can csunixmount with ease!

Part 7: More on Linux (Do this part with your laptop)

You'll spend the rest of your time learning more about Linux and the more powerful editors emacs/vi.
  1. Review the Unix command summary. Then, open a terminal and practice entering all of the "Usage Examples" (from the "Unix command summary" page) to see what each command does (the commands need to be done in order). Use "ls" frequently to see what effect the commands are having.
  2. In your VM, run csunixmount (if you haven't done so yet), and cd to ~/csunix/ic210/lab01.
  3. Create lab01.cpp as follows:
    #include <iostream>
    using namespace std;
    
    int main()
    {
       cout << "Hello World!" << endl;
       cout << "This is a 1!" << endl;
    
       return 0;
    }
    
  4. Modify the program lab01.cpp so that it's output matches what's shown exactly!
    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! Use editor commands! 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
    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!

Part 8: Submit this lab01.cpp to the submission system

TEST TEST TEST your code before proceeding

  1. BEFORE you submit your code, look very carefully at the required output (above), and compare it to your output. Does it match exactly? Throughout this course, it will be very important that you TEST your code to see if it works properly. Normally, that will mean (a) testing it on a variety of inputs and (b) ensuring that it produces precisely the desired output in each case. Right now, your program always does the same thing (there is no "input"), so you just need to verify that the output is correct. "Correct" output means having exactly the right spacing, "newlines", capitalization, punctuation, etc.

In your Laptop

  1. (Install the submit script) Follow this instruction in the resources to install the submit script.
  2. Cd to the directory that contains the lab01.cpp file.
    cd ~/csunix/ic210/lab01
  3. Submit your program by giving the following command:
    ~/bin/submit -c=IC210 -p=Lab01Laptop lab01.cpp
  4. Using your web browser, check the submission server and check your work. 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.
  5. Note that for some IC210 assignments, the "submit" system will only allow you to make a limited number of submissions. This will be to encourage you to check your program carefully (test it yourself) before you submit.

In your lab machine

  1. (Install the submit script) Follow this instruction in the resources to install the submit script.
  2. Cd to the directory that contains the lab01.cpp file (note the difference of the directory).
    cd ~/ic210/lab01
  3. Submit your program by giving the following command (note the difference of the project name).
    ~/bin/submit -c=IC210 -p=Lab01Labmachine lab01.cpp
  4. Check the submission server to see if you submitted your work successfully.

Due: before class starts, this Friday