The purpose of this assignment is to familiarize you with using the computer and with the mechanics of preparing and submitting assignment solutions. This assignment carries no grade, but you must do the electronic submission. Your goal this week is to learn to use emacs for editing files, gcc for compiling programs, and submit for submitting assignments.

Your assignment is to create, compile, and run 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;
}

Completing this assignment involves the following steps.

• Log in to a SUN Unix machine. If you're the least bit unsure about using a computer, use one of the machines in room 101 in the CS building. Detailed instructions on what to do on these machines are given below, and there will be trained staff there to answer your questions this week. If you're used to using arizona via a telnet session, feel free to do so, but you will need to adjust the directions that follow as indicated.

• When you log in, you will be asked for your username and password. Then you may be asked to choose a desktop environment. Choose the "Common Desktop Environment". It is a graphical user interface based on X Windows. You should see a "Control Panel" along the bottom of the screen, and a "File Manager" window somewhere else on the screen. A tutorial window may also appear. There are lots of "Help" menus; click on a few to see what's available. If you were unable to log in, find a lab TA and they will assist you.
• To open a terminal window, click the right mouse button once (and release) in an empty area of the display, then click the left mouse button on the menu entry for "Tools", then click the left mouse button on the sub-menu entry for "Terminal".

• You should now have a "Terminal" window somewhere on the screen. It will have a command prompt that looks something like:

  phoenix.Princeton.EDU% 

  Don't worry if it looks a little different. You can enter a command by typing it in the Terminal window followed by the "Enter" or "Return" key.
• For your first command, type the text in bold at the command prompt:

  phoenix.Princeton.EDU% source /u/cs126/bin/setup126-s01

  This customizes several Unix tools specifically for COS 126. (Specifically, it adds /u/cs126/bin to your path, copies our .emacs file to your directory, and creates a dummy web page for you, unless you already have one. If most of this sounds like gibberish, don't worry about it.)

• Now you are ready to write your first program. To begin the process, type

  phoenix.Princeton.EDU% xemacs hello.c &

  to create a window for the xemacs text editor, ready for you to type in the file hello.c. The & means to run xemacs in the background, so that you can type other commands without leaving xemacs. The xemacs editor is a bit more complicated than the standard Text Editor on the desktop, but much more powerful, and includes special features designed for writing C programs. If you've used text editors before, you will know how to use xemacs. Just use the pull-down menus and the mouse. You can also launch a tutorial from the Help menu.

  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 a file named hello.c.

Working from home. If you are working in a telnet session, you will not be able to use xemacs. Use the command "emacs hello.c" instead. The emacs editor is very similar to xemacs, but lacks the nice graphical user interface.

• Now type

  phoenix.Princeton.EDU% 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. 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.
• Type

  phoenix.Princeton.EDU% a.out

  in the Terminal window. 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 by typing the following command:

  phoenix.Princeton.EDU% submit126 0 hello.c

• If this were a real assignment, you might want to check that everything was submitted properly. To list all the files that you have submitted already for Assignment 0, type

  phoenix.Princeton.EDU% submit126 0

• To get a printed copy of your program, type the following command in the Terminal window.

  phoenix.Princeton.EDU% enscript126 hello.c

in the Terminal window.

Working from home. The enscript command prints to the printer in the CS lab. The easiest way to use your own printer instead is to ftp the desired file to your computer, and then print as usual under Windows or Mac OS.

• The final part of the assignment is to browse the COS 126 Web pages. To do this type

  phoenix.Princeton.EDU% netscape &

  and click on netscape's Open button, and enter

  courseinfo.princeton.edu/courses/COS126_S2001/

  in the Location box. 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.

  Working from home. You will not be able to run netscape from a telnet sessions. Instead use the web browser on your computer.

• To log out, position the mouse over the background, i.e., not over any windows, click the right mouse button, and select "Logout". Don't forget to log out!

  Working from home. Type the command "logout" when you are finished.