The purpose of this assignment is to familiarize you with the mechanics of preparing and submitting assignment solutions. This assignment carries no grade, but you must do the electronic submission. Follow these instructions if you wish to use the Mac OS X operating system. We provide different instructions if you prefer to use a Windows machine or the arizona workstations. Your goal this week is to learn to use Project Builder for editing files and gcc for compiling programs.

Your assignment is to create, compile, run and submit three short C programs. In addition, you will edit and submit a descriptive file called readme.txt with each of your assignments. (Instructions for the readme file are on the checklist for each assignment.)

PROGRAM 1 hello.c : Create, compile, run and submit the following extension of everybody's first C program.

#include <stdio.h>

int main(void) {
    int num;
    printf("Hello world! Give me an integer:\n");
    scanf("%d", &num);
    printf("Thanks! I've always been fond of %d.\n", num);
    return 0;
}

PROGRAM 2 hello-while.c : Create, compile, run and submit Hello World Exercise #5.

PROGRAM 3 hello-if.c : Create, compile, run and submit Hello World Exercise #6.

Completing this assignment involves a number of steps that are described below. The instructions refer to Program 1, but will be the same for Programs 2 and 3.

• Install the OS X operating system and the Developer Tools by following the instructions at this link. You do not need to install the other software mentioned to complete this assignment, but you will need it for future assignments so you might as well do it now.

• Open a terminal window. If you followed the installation instructions, you can do this by double clicking the appropriate icon on your Dock.

Now you are ready to write your first program. To begin the process, open up the Project Builder editor.

• Enter the C program exactly as it appears above. If you omit even a semicolon, the program won't work. Use the Tab key to get the proper indentation.

• When you're done, save the program in your Home directory and name the file hello.c.

• It is now time to convert your C program into machine executable code. Type the bold text below

  [localhost:~] wayne% gcc126 hello.c

  in the Terminal window. This command runs the C compiler, gcc, which compiles hello.c and leaves an executable file named a.out in your directory. We use gcc126 instead of gcc to ask the compile to output additional warnings: novice and veteran programmers will find this invaluable. If gcc complains in some way, you mistyped something, and you should check your program carefully. Ask for help if you can't see the mistake.

• In the Terminal window, type

  [localhost:~] wayne% a.out

  This command executes your program. You should get

  Hello world! Give me an integer:

  in the Terminal window. Then nothing will happen. You must type an integer (say, 5), and hit Enter, then you will get

  Thanks! I've always been fond of 5.

  and the program should terminate. You may need to repeat this edit-compile-execute cycle a few times before it all goes smoothly.

• Once you have hello.c working, submit it via the Web. To do this, launch your favorite browser and go to the COS 126 web page:

  http://www.princeton.edu/~cs126

  choose the Assignment Submission menu option, and follow the instructions provided.

• You will receive an email confirmation of your submission.

• The final part of the assignment is to browse the COS 126 Web pages. The address is:

  http://www.princeton.edu/~cs126

  Cruise around the COS 126 Web site; it is essential that you understand what's where and how to get to it. Be sure to fill out the online questionnaire. Also make sure you find the "Assignment 0 Checklist" page, and also be sure to read the COS 126 Collaboration Policy.