path: root/talermerchantdemos/blog/articles/scrap1_46.html

<!-- This is the second edition of Free Software, Free Society: Selected Essays of Richard M. Stallman.

Free Software Foundation

51 Franklin Street, Fifth Floor

Boston, MA 02110-1335
Copyright C 2002, 2010 Free Software Foundation, Inc.
Verbatim copying and distribution of this entire book are permitted
worldwide, without royalty, in any medium, provided this notice is
preserved. Permission is granted to copy and distribute translations
of this book from the original English into another language provided
the translation has been approved by the Free Software Foundation and
the copyright notice and this permission notice are preserved on all
copies.

ISBN 978-0-9831592-0-9
Cover design by Rob Myers.

Cover photograph by Peter Hinely.
 -->


 <a name="Freedom-or-Power_003f">
 </a>
 <a name="Appendix-A_003a-A-Note-on-Software">
 </a>
 <h1 class="unnumbered">
  <span class="roman">
   Appendix A: A Note on Software
  </span>
 </h1>
 <p>
  Written by Richard E. Buckman and Joshua Gay.
  <br/>
 </p>
 <p>
  This section is intended for people who have little or no knowledge of
the technical aspects of computer science. It is not necessary to read
this section to understand the essays and speeches presented in this
book; however, it may be helpful to those readers not familiar with
some of the jargon that comes with programming and computer science.
 </p>
 <p>
  A computer
  <em>
   programmer
  </em>
  writes software, or computer programs. A
program is more or less a recipe with
  <em>
   commands
  </em>
  to tell the
computer what to do in order to carry out certain tasks. You are more
than likely familiar with many different programs: your Web browser,
your word processor, your email client, and the like.
 </p>
 <p>
  A program usually starts out as
  <em>
   source code
  </em>
  . This higher-level
set of commands is written in a
  <em>
   programming language
  </em>
  such as C
or Java. After that, a tool known as a
  <em>
   compiler
  </em>
  translates this
to a lower-level language known as
  <em>
   assembly language
  </em>
  . Another
tool known as an
  <em>
   assembler
  </em>
  breaks the assembly code down to the
final stage of
  <em>
   machine language
  </em>
  —the lowest level—which the
computer understands
  <em>
   natively
  </em>
  .
 </p>
 <img alt="code" src="/essay/Appendix_A:_A_Note_on_Software/data/code.jpg">
  <p>
   For example, consider the
“hello world” program, a common first program for people learning C,
which (when compiled and executed) prints “Hello World!” on the screen.
   <a href="#FOOT54" name="DOCF54">
    (54)
   </a>
  </p>
  <table>
   <tr>
    <td>
    </td>
    <td>
     <pre class="smallexample">int main(){
    printf(''Hello World!'');
    return 0;
}
</pre>
    </td>
   </tr>
  </table>
  <p>
   In the Java programming language the same program would
be written like this:
  </p>
  <table>
   <tr>
    <td>
    </td>
    <td>
     <pre class="smallexample">public class hello {
    public static void main(String args[]) {
        System.out.println(''Hello World!'');
    }
}
</pre>
    </td>
   </tr>
  </table>
  <p>
   However, in machine language, a small section of it may look similar to
this:
  </p>
  <table>
   <tr>
    <td>
    </td>
    <td>
     <pre class="smallexample">1100011110111010100101001001001010101110
0110101010011000001111001011010101111101
0100111111111110010110110000000010100100
0100100001100101011011000110110001101111
0010000001010111011011110111001001101100
0110010000100001010000100110111101101111
</pre>
    </td>
   </tr>
  </table>
  <p>
   The above form of machine language is the most basic representation
known as binary. All data in computers is made up of a series of
0-or-1 values, but a person would have much difficulty understanding
the data. To make a simple change to the binary, one would have to
have an intimate knowledge of how a particular computer interprets the
machine language. This could be feasible for small programs like the
above examples, but any interesting program would involve an
exhausting effort to make simple changes.
  </p>
  <p>
   As an example, imagine that we wanted to make a change to our “Hello
World” program written in C so that instead of printing “Hello World”
in English it prints it in French. The change would be simple; here is
the new program:
  </p>
  <table>
   <tr>
    <td>
    </td>
    <td>
     <pre class="smallexample">int main() {
    printf(''Bonjour, monde!'');
    return 0;
}
</pre>
    </td>
   </tr>
  </table>
  <p>
   It is safe to say that one can easily infer how to change the program
written in the Java programming language in the same way. However,
even many programmers would not know where to begin if they wanted to
change the binary representation. When we say “source code,” we do
not mean machine language that only computers can understand—we are
speaking of higher-level languages such as C and Java. A few other
popular programming languages are C++, Perl, and Python. Some are
harder than others to understand and program in, but they are all much
easier to work with compared to the intricate machine language
they get turned into after the programs are compiled and assembled.
  </p>
  <p>
   Another important concept is understanding what an
   <em>
    operating
system
   </em>
   is. An operating system is the software that handles input and
output, memory allocation, and task scheduling. Generally one
considers common or useful programs such as the
   <em>
    Graphical User
Interface
   </em>
   (GUI) to be a part of the operating system. The GNU/Linux
operating system contains a both GNU and non-GNU software, and a
   <em>
    kernel
   </em>
   called
   <em>
    Linux
   </em>
   . The kernel handles low-level tasks
that applications depend upon such as input/output and task
scheduling. The GNU software comprises much of the rest of the
operating system, including GCC, a general-purpose compiler for many
languages; GNU Emacs, an extensible text editor with many, many
features; GNOME, the GNU desktop; GNU libc, a library that all
programs other than the kernel must use in order to communicate with
the kernel; and Bash, the GNU command interpreter that reads your
command lines. Many of these programs were pioneered by Richard
Stallman early on in the GNU Project and come with any modern
GNU/Linux operating system.
  </p>
  <p>
   It is important to understand that even if
   <em>
    you
   </em>
   cannot
change the source code for a given program, or directly use all these
tools, it is relatively easy to find someone who can. Therefore, by
having the source code to a program you are usually given the power to
change, fix, customize, and learn about a program—this is a power that
you do not have if you are not given the source code. Source
code is one of the requirements that makes a piece of software
   <em>
    free
   </em>
   . The other requirements will be found along with the
philosophy and ideas behind them in this collection.
  </p>
  <div class="footnote">
   <hr>
    <h3>
     Footnotes
    </h3>
    <h3>
     <a href="#DOCF54" name="FOOT54">
      (54)
     </a>
    </h3>
    <p>
     In other programming languages, such as
Scheme, the
     <em>
      Hello World
     </em>
     program is usually not your first program.
In Scheme you often start with a program like this:
    </p>
    <table>
     <tr>
      <td>
      </td>
      <td>
       <pre class="smallexample">(define (factorial n)
  (if (= n 0)
      1
      (* n (factorial (- n 1)))))
</pre>
      </td>
     </tr>
    </table>
    <p>
     This computes the factorial of a number; that is, running
     <code>
      (factorial 5)
     </code>
     would output 120, which is computed by doing
5 * 4 * 3 * 2 * 1 * 1.
    </p>
   </hr>
  </div>
  <hr size="6"/>
 </img>