Polish Preface

Polish the English text of `tutorial/en/0-Preface.md`, and:

* Add Level 1 title ("Preface").
* Replaces smiles with markdown emojis.
* Fix titles casing using Chicago Manual of Style capitalization rules:
  https://capitalizemytitle.com/style/chicago#
* Convert inline-link to reference-style links (DRY!).
* Add a few links to external references.

Author: tajmone

tutorial/en/0-Preface.md

@@ -1,104 +1,126 @@
-This series of articles is a tutorial for building a C compiler from scratch.
+# Preface
 
-I lied a little in the above sentence: it is actually an _interpreter_ instead
-of _compiler_. I lied because what the hell is a "C interpreter"? You will
-however, understand compilers better by building an interpreter.
+This is multi-part tutorial on how to build a C compiler from scratch.
 
-Yeah, I wish you can get a basic understanding of how a compiler is
-constructed, and realize it is not that hard to build one. Good Luck!
+Well, I lied a little in the previous sentence: it's actually an _interpreter_,
+not a _compiler_. I had to lie, because what on earth is a "C interpreter"?
+You will however gain a better understanding of compilers by building an
+interpreter.
 
-Finally, this series is written in Chinese in the first place, feel free to
-correct me if you are confused by my English. And I would like it very much if
-you could teach me some "native" English :)
+Yeah, I want to provide you with a basic understanding of how a compiler is
+constructed, and realize that it's not that hard to build one, after all.
+Good Luck!
 
-We won't write any code in this chapter, feel free to skip it if you are
-desperate to see some code...
+This tutorial was originally written in Chinese, so feel free to correct me if
+you're confused by my English. Also, I would really appreciate it if you could
+teach me some "native" English. :smile:
 
-## Why you should care about compiler theory?
+We won't be writing any code in this chapter; so if you're eager to see some code, feel free to skip it.
 
-Because it is **COOL**!
 
-And it is very useful. Programs are built to do something for us, when they
-are used to translate some forms of data into another form, we can call them
-a compiler. Thus by learning some compiler theory we are trying to master a very
-powerful technique of solving problems. Isn't that cool enough to you?
+## Why Should I Care about Compiler Theory?
+
+Because it's **COOL**!
+
+And it's also very useful. Programs are designed to do something for us; when
+they are used to translate some form of data into another form, we can call
+them compilers. Thus, by learning some compiler theory, we are trying to
+master a very powerful problem solving technique. Doesn't this sound cool
+enough to you?
+
+People used to say that understanding how a compiler works would help you to
+write better code. Some would argue that modern compilers are so good at
+optimizing that you shouldn't care any more. Well, that's true, most people
+don't need to learn compiler theory to improve code performance — and by "most
+people" I mean _you_!
 
-People used to say understanding how a compiler works would help you to write
-better code. Some would argue that modern compilers are so good at
-optimization that you should not care any more. Well, that's true, most people
-don't need to learn compiler theory only to improve the efficency of the code.
-And by most people, I mean you!
 
 ## We Don't Like Theory Either
 
-I have always been in awe of compiler theory because that's what makes
-programing easy. Anyway can you imaging building a web browser in only
-assembly language? So when I got a chance to learn compiler theory in college,
-I was so excited! And then... I quit, not understanding what that it.
+I've always been in awe of compiler theory because that's what makes programing
+easy. Anyway, can you imagine building a web browser entirely in assembly
+language? So when I got a chance to learn compiler theory in college, I was so
+excited! And then ... I quit! And left without understanding what it's all
+about.
 
-Normally a course of compiler will cover:
+Normally compiler course covers the following topics:
 
-1. How to represent syntax (such as BNF, etc.)
-2. Lexer, with somewhat NFA(Nondeterministic Finite Automata),
-   DFA(Deterministic Finite Automata).
-3. Parser, such as recursive descent, LL(k), LALR, etc.
+1. How to represent syntaxes (i.e. BNF, etc.)
+2. Lexers, using NFA (Nondeterministic Finite Automata) and
+   DFA (Deterministic Finite Automata).
+3. Parsers, such as recursive descent, LL(k), LALR, etc.
 4. Intermediate Languages.
 5. Code generation.
 6. Code optimization.
 
-Perhaps more than 90% students will not care anything beyond the parser, and
-what's more, we still don't know how to build a compiler! Even after all the
-effort learning the theories. Well the main reason is that what "Compiler
-Thoery" trys to teach is "How to build a parser generator", namely a tool that
-consumes syntax gramer and generates a compiler for you. lex/yacc or
-flex/bison or things like that.
+Perhaps more than 90% of the students won't really care about any of that,
+except for the parser, and what's more, we'd still won't know how to actually
+build a compiler! even after all the effort of learning the theory. Well, the
+main reason is that what "Compiler Theory" tries to teach is "how to build a
+parser generator" — i.e. a tool that consumes a syntax grammar and generates a
+compiler for you, like lex/yacc or flex/bison, or similar tools.
+
+These theories try to teach us how to solve the general challenges of
+generating compilers automatically. Once you've mastered them, you're able to
+deal with all kinds of grammars. They are indeed useful in the industry.
+Nevertheless, they are too powerful and too complicated for students and most
+programmers. If you try to read lex/yacc's source code you'll understand what
+I mean.
 
-These theories try to teach us how to solve the general problems of generating
-compilers automatically. That means once you've mastered them, you are able to
-deal with all kinds of grammars. They are indeed useful in industry.
-Nevertheless they are too powerful and too complicated for students and most
-programmers. You will understand that if you try to read lex/yacc's source
-code.
+The good news is that building a compiler can be much simpler than you ever
+imagined. I won't lie, it's not easy, but definitely not hard.
 
-Good news is building a compiler can be much simpler than you ever imagined.
-I won't lie, not easy, but definitely not hard.
 
-## Birth of this project
+## How This Project Began
 
-One day I came across the project [c4](https://github.com/rswier/c4) on
-Github. It is a small C interpreter which is claimed to be implemented by only
-4 functions. The most amazing part is that it is bootstrapping (that interpret
-itself). Also it is done with about 500 lines!
+One day I came across the project [c4] on Github, a small C interpreter
+claiming to be implemented with only 4 functions. The most amazing part is
+that it's [bootstrapping]  (i.e. it can interpret itself). Furthermore, it's
+being done in around 500 lines of code!
 
-Meanwhile I've read a lot of tutorials about compiler, they are either too
-simple(such as implementing a simple calculator) or using automation
-tools(such as flex/bison). c4 is however implemented all from scratch. The
-sad thing is that it try to be minimal, that makes the code quite a mess, hard
-to understand. So I started a new project to:
+Meanwhile, I've read many tutorials on compilers design, and found them to be
+either too simple (such as implementing a simple calculator) or using
+automation tools (such as flex/bison). [C4], however, is implemented entirely
+from scratch. The sad thing is that it aims to be "an exercise in minimalism,"
+which makes the code quite messy and hard to understand. So I started a new
+project, in order to:
 
-1. Implement a working C compiler(interpreter actually)
-2. Write a tutorial of how it is built.
+1. Implement a working C compiler (an interpreter, actually).
+2. Write a step-by-step tutorial on how it was built.
 
-It took me 1 week to re-write it, resulting 1400 lines including comments. The
-project is hosted on Github: [Write a C Interpreter](https://github.com/lotabout/write-a-C-interpreter).
+It took me one week to re-write it, resulting in 1400 lines of code (including
+comments). The project is hosted on Github: [Write a C Interpreter].
 
-Thanks rswier for bringing us a wonderful project!
+Thanks [@rswier] for sharing with us [c4], it's such a wonderful project!
 
-## Before you go
 
-Implementing a compiler could be boring and it is hard to debug. So I hope you
-can spare enough time studying, as well as type the code. I am sure that you
-will feel a great sense of accomplishment just like I do.
+## Before You Begin
+
+Implementing a compiler can be boring and hard to debug. So I hope you can
+spare enough time studying, and typing code. I'm sure that you will feel a
+great sense of accomplishment, just like I do.
+
 
 ## Good Resources
 
-1. [Let’s Build a Compiler](http://compilers.iecc.com/crenshaw/): a very good
-   tutorial of building a compiler for fresh starters.
-2. [Lemon Parser Generator](http://www.hwaci.com/sw/lemon/): the parser
-   generator that is used in SQLite. Good to read if you want to understand
-   compiler theory with code.
+1. _[Let’s Build a Compiler]_: a very good tutorial of building a compiler,
+    written for beginners.
+2. [Lemon Parser Generator]: the parser generator used by SQLite.
+   Good to read if you want to understand compiler theory with code.
+
+In the end, I am just a person with a general level of expertise, so there
+will inevitably be some mistakes in my articles and code (and also in my
+English). Feel free to correct me!
+
+I hope you'll enjoy it.
 
-In the end, I am human with a general level, there will be inevitably wrong
-with the articles and codes(also my English). Feel free to correct me!
+<!-----------------------------------------------------------------------------
+                               REFERENCE LINKS
+------------------------------------------------------------------------------>
 
-Hope you enjoy it.
+[@rswier]: https://github.com/rswier "Visit @rswier's GitHub profile"
+[bootstrapping]: https://en.wikipedia.org/wiki/Bootstrapping_(compilers) "Wikipedia » Bootstrapping (compilers)"
+[c4]: https://github.com/rswier/c4 "Visit the c4 repository on GitHub"
+[Lemon Parser Generator]: http://www.hwaci.com/sw/lemon/ "Visit Lemon homepage"
+[Let’s Build a Compiler]: http://compilers.iecc.com/crenshaw/ "15-part tutorial series, by Jack Crenshaw"
+[Write a C Interpreter]: https://github.com/lotabout/write-a-C-interpreter "Visit the 'Write a C Interpreter' repository on GitHub"