bitcoinbook/preface.asciidoc

[preface]
== Preface

=== Writing the Bitcoin Book

I first stumbled upon bitcoin in mid-2011. My immediate reaction was more or less "Pfft! Nerd money!" and I ignored it for another 6 months, failing to grasp its importance. This is a reaction which I have seen repeated among many of the smartest people I know, which gives me some consolation. The second time I came across bitcoin in a mailing list discussion, I decided to read the white paper written by Satoshi Nakamoto, to study the authoritative source and see what it was all about. I still remember the moment I finished reading those 9 pages, when I realized that bitcoin was not simply a digital currency, but a network of trust that could also provide the basis for so much more than just currencies. That realization: "This isn't money, it's a de-centralized trust network", started me on a four month journey to devour every scrap of information about bitcoin I could find. I became obsessed and enthralled, spending twelve or more hours each day glued to a screen, reading, writing, coding and learning as much as I could. I emerged from this state of fugue, more than 20 lbs lighter from lack of consistent meals, determined to dedicate myself to working on bitcoin. 

Two years later, after creating a number of small startups to explore various bitcoin-related services and products, I decided that it was time to write my first book. Bitcoin was the topic that had driven me into a frenzy of creativity, consumed my thoughts and is the most exciting technology I have encountered since the Internet. It was now time to share my discovery of this amazing technolgy and my passion with a broader audience. This is the bitcoin book.

=== Intended Audience

This book is mostly intended for coders. If you can use a programming language, this book will teach you how cryptographic currencies work, how to use them and how to develop software that works with them. The first few chapters are also suitable as an in-depth introduction to bitcoin for non-coders - those trying to understand the inner workings of bitcoin and cryptocurrencies. The examples are illustrated in Python and on the command-line of a Unix-like operating system such as Linux. 

=== Early-Release Note

The early release version of the book is a *raw and rough draft* and will change regularly. New chapters will be added as they are drafted and there will be plenty of changes to the content, examples and diagrams. There will be factual and technical errors in the early release and some of the examples may not work or refer to obsolete versions of the code. Nevertheless, I hope you will enjoy the content and find it useful. I also hope that you will take the opportunity to "fork" the source code of the book and provide feedback by creating a pull request or submitting a patch. I present this work in the spirit of Cunningham's Law, named after the inventor of the wiki, Ward Cunningham:

.Cunningham's Law
====
_The best way to get the right answer on the Internet is not to ask a question, it's to post the wrong answer_
====

I hope you can help me find and publish the "right answer" by the time this book is ready to print.

=== Conventions Used in This Book

The following typographical conventions are used in this book:

_Italic_:: Indicates new terms, URLs, email addresses, filenames, and file extensions.

+Constant width+:: Used for program listings, as well as within paragraphs to refer to program elements such as variable or function names, databases, data types, environment variables, statements, and keywords.

**`Constant width bold`**:: Shows commands or other text that should be typed literally by the user.

_++Constant width italic++_:: Shows text that should be replaced with user-supplied values or by values determined by context.


[TIP]
====
This icon signifies a tip, suggestion, or general note.
====

[WARNING]
====
This icon indicates a warning or caution.
====

=== Using Code Examples

This book is here to help you get your job done. In general, if example code is offered with this book, you may use it in your programs and documentation. You do not need to contact us for permission unless you’re reproducing a significant portion of the code. For example, writing a program that uses several chunks of code from this book does not require permission. Selling or distributing a CD-ROM of examples from O’Reilly books does require permission. Answering a question by citing this book and quoting example code does not require permission. Incorporating a significant amount of example code from this book into your product’s documentation does require permission.

We appreciate, but do not require, attribution. An attribution usually includes the title, author, publisher, and ISBN. For example: “_Book Title_ by Some Author (O’Reilly). Copyright 2012 Some Copyright Holder, 978-0-596-xxxx-x.”

If you feel your use of code examples falls outside fair use or the permission given above, feel free to contact us at pass:[<email>permissions@oreilly.com</email>].

=== Safari® Books Online

[role = "safarienabled"]
[NOTE]
====
pass:[<ulink role="orm:hideurl:ital" url="http://my.safaribooksonline.com/?portal=oreilly">Safari Books Online</ulink>] is an on-demand digital library that delivers expert pass:[<ulink role="orm:hideurl" url="http://www.safaribooksonline.com/content">content</ulink>] in both book and video form from the world&#8217;s leading authors in technology and business.
====

Technology professionals, software developers, web designers, and business and creative professionals use Safari Books Online as their primary resource for research, problem solving, learning, and certification training.

Safari Books Online offers a range of pass:[<ulink role="orm:hideurl" url="http://www.safaribooksonline.com/subscriptions">product mixes</ulink>] and pricing programs for pass:[<ulink role="orm:hideurl" url="http://www.safaribooksonline.com/organizations-teams">organizations</ulink>], pass:[<ulink role="orm:hideurl" url="http://www.safaribooksonline.com/government">government agencies</ulink>], and pass:[<ulink role="orm:hideurl" url="http://www.safaribooksonline.com/individuals">individuals</ulink>]. Subscribers have access to thousands of books, training videos, and prepublication manuscripts in one fully searchable database from publishers like O’Reilly Media, Prentice Hall Professional, Addison-Wesley Professional, Microsoft Press, Sams, Que, Peachpit Press, Focal Press, Cisco Press, John Wiley & Sons, Syngress, Morgan Kaufmann, IBM Redbooks, Packt, Adobe Press, FT Press, Apress, Manning, New Riders, McGraw-Hill, Jones & Bartlett, Course Technology, and dozens pass:[<ulink role="orm:hideurl" url="http://www.safaribooksonline.com/publishers">more</ulink>]. For more information about Safari Books Online, please visit us pass:[<ulink role="orm:hideurl" url="http://www.safaribooksonline.com/">online</ulink>].

=== How to Contact Us

Please address comments and questions concerning this book to the publisher:

++++
<simplelist>
<member>O’Reilly Media, Inc.</member>
<member>1005 Gravenstein Highway North</member>
<member>Sebastopol, CA 95472</member>
<member>800-998-9938 (in the United States or Canada)</member>
<member>707-829-0515 (international or local)</member>
<member>707-829-0104 (fax)</member>
</simplelist>
++++

We have a web page for this book, where we list errata, examples, and any additional information. You can access this page at link:$$http://shop.oreilly.com/product/0636920032281.do$$[].


To comment or ask technical questions about this book, send email to pass:[<email>bookquestions@oreilly.com</email>].

For more information about our books, courses, conferences, and news, see our website at link:$$http://www.oreilly.com$$[].

Find us on Facebook: link:$$http://facebook.com/oreilly$$[]

Follow us on Twitter: link:$$http://twitter.com/oreillymedia$$[]

Watch us on YouTube: link:$$http://www.youtube.com/oreillymedia$$[]
++++
<?hard-pagebreak?>
++++

=== Quick Glossary

This quick glossary contains many of the terms used in relation to bitcoin. These terms are used throughout the book, so bookmark this for a quick reference and clarification.

address (aka public key)::
((("bitcoin address")))
((("address", see="bitcoin address")))
((("public key", see="bitcoin address")))
	A bitcoin address looks like +1DSrfJdB2AnWaFNgSbv3MZC2m74996JafV+, they always start with a one. You can have as many as you like, share them so people can send you coins. 

bitcoin::
((("bitcoin"))) 
    The name of the currency unit (the coin), the network and the software

block::
((("block")))
	A grouping of transactions, marked with a timestamp, and a fingerprint of the previous block. The block header is hashed to find a proof-of-work, thereby validating the transactions. Valid blocks are added to the main blockchain by network consensus.

blockchain::
((("blockchain")))
		A list of validated blocks, each linking to its predecessor all the way to the genesis block.
	
confirmations::
((("confirmations")))
		Once a transaction is included in a block, it has "one confirmation". As soon as _another_ block is mined on the same blockchain, the transaction has two confirmations etc. Six or more confirmations is considered final. 

difficulty::
((("difficulty")))
	A network-wide setting that controls how much computation is required to find a proof-of-work.

difficulty target::
((("target difficulty")))
 	A difficulty at which all the computation in the network will find blocks approximately every 10 minutes.

difficulty re-targetting::
((("difficulty re-targetting")))
	A network-wide re-calculation of the difficulty which occurs once every 2106 blocks and considers the hashing power of the previous 2106 blocks.
	
fees::
((("fees")))
	An excess amount included in each transaction as a network fee or additional reward to the miner who finds the proof-of-work for the new block. Currently 0.5 mBTC minimum.

hash::
((("hash")))
	A digital fingerprint of some binary input.

genesis block::
((("genesis block")))
	The first block in the blockchain, used to initialize the crypto-currency
	
miner::
((("miner")))
	A network node that finds valid proof-of-work for new blocks, by repeated hashing

network::
((("network")))
	A peer-to-peer network that propagates transactions and blocks to every bitcoin node on the network. 
	
proof-of-work::
((("proof-of-work")))
	A piece of data that requires significant computation to find. In bitcoin, miners must find a numeric solution to the SHA256 algorithm that meets a network wide target, the difficulty target. 

reward::
((("reward")))
	An amount included in each new block as a reward by the network to the miner who found the proof-of-work solution. It is currently 25BTC per block.

secret key (aka private key)::
((("secret key")))
((("private key", see="secret key")))
	The secret number that unlocks bitcoins sent to the corresponding address.
	
transaction::
((("transaction")))
	In simple terms, a transfer of bitcoins from one address to another. More precisely, a transaction is a signed data structure expressing a transfer of value. Transactions are transmitted over the bitcoin network, collected by miners and included into blocks, made permanent on the blockchain.

wallet::
((("wallet"))) 
	Software that holds all your addresses. Use it to send bitcoin and manage your keys.