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diff --git a/talermerchantdemos/blog/articles/scrap1_46.html b/talermerchantdemos/blog/articles/scrap1_46.html new file mode 100644 index 0000000..914a985 --- /dev/null +++ b/talermerchantdemos/blog/articles/scrap1_46.html @@ -0,0 +1,292 @@ +<!-- 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> + |