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======Exercise 1: Dust Off That Compiler======

   Here is a simple first program you can make in C:
int main(int argc, char *argv[])
{
    puts("Hello world.");

    return 0;
}

   You can put this into a ex1.c then type:
$ make ex1
cc     ex1.c   -o ex1

   Your computer may use a slightly different command, but the end result
   should be a file named ex1 that you can run.

======What You Should See======

   You can now run the program and see the output.
$ ./ex1
======Hello world.======

   If you don't then go back and fix it.

======How To Break It======

   In this book I'm going to have a small section for each program on how
   to break the program. I'll have you do odd things to the programs, run
   them in weird ways, or change code so that you can see crashes and
   compiler errors.

   For this program, rebuild it with all compiler warnings on:
$ rm ex1
$ CFLAGS="-Wall" make ex1
cc -Wall    ex1.c   -o ex1
ex1.c: In function 'main':
ex1.c:3: warning: implicit declaration of function 'puts'
$ ./ex1
======Hello world.======
$

   Now you are getting a warning that says the function "puts" is
   implicitly declared. The C compiler is smart enough to figure out what
   you want, but you should be getting rid of all compiler warnings when
   you can. How you do this is add the following line to the top of ex1.c
   and recompile:
#include <stdio.h>

   Now do the make again like you just did and you'll see the warning go
   away.

======Extra Credit======

     * Open the ex1 file in your text editor and change or delete random
       parts. Try running it and see what happens.
     * Print out 5 more lines of text or something more complex than hello
       world.
     * Run man 3 puts and read about this function and many others.


   Copyright (C) 2010 Zed. A. Shaw

   Credits