Computer Science Books

I bought this book because I'm interested in cryptology but do not have the time to dig deep into specialist books. The book did not dissapoint me - it is well written, not too technical but doesn't 'dumb down' the essence of cryptology too much. The only reason why I wouldn't want to give it 5 stars is that it is a bit dated. Written quite obviously before 9/11, it is a bit too optimistic on the outcome of the battle between code makers and code breakers.

A good book, fun to read, and relatively easy to grasp.

"The Code Book" presents readers with a beautifully composed account of the history of cryptography. It is written in such a way to keep the technically inclined satisfied without overloading the average reader. Singh does an excellent job at presenting technical material.

This book maintains a high level of drama and excitement, constantly sparking imagination and occasionally encouraging readers to try their own hand at cryptography.

I definitely recommend this book to anyone remotely interested in history, information technology, or politics. It's an excellent read.

More than a history of cryptography, this book could be called a set of
stories about the topic. Which is not a demerit, on the contrary, adds
amenity to a topic that on one hand is interesting and entertaining (who
doesn't like to keep one's secrets and break those of others?) but on
the other hand may be hard (the mathematics and algorithms). The author
copes very well with the fun part and really quite well with the other
part, taking into account that this is not a text book but a informational
and even recreational book.
A reader not familiar with algorithms or computing may still be able to
grasp most of the ideas and every reader will surely enjoy of the well
documented stories on which the book is built. The language is clear
and simple (I am not an English native speaker and nevertheless I can
read it quite easily) so I think that even children of about 12 y.o.
and up may find the book interesting.

In the Code Book, Simon Singh takes us on a fascinating journey through cryptography from ancient Egypt to to the modern. He touches on many historical figures and their contributions to modern day cryptography. Personalities such as: Charles Babbage (the grandfather of computing), Alan Turing (creator of the Turing Machine, the father of modern computer science), Ronald Rivest, Adi Shamir, and Leon Adleman (the men behind RSA encryption), and Phil Zimmermann.

This book was enlightening as it put the cryptography mechanisms we employ today into a historical context while describing their complex inner workings and presenting the rich history that lies behind all innovation. Like other reviewers, I was also disappointed that the book came to a close so soon. I'm looking forward to reading Singh's other books.

You will learn all about how secret communications through code have created the history of europe, middle east and other nations. Just get this book.

I bought this book as a present for my brother's birthday, but when I got it, I had a hard time putting it down. I'm not much of a trekkie but this is a really fun book.

this book is a complete and detailed accounts for all star trek series and movies...a must for all collector of star trek.

You want to look up something about trek,get this book. it is ridiculously packed full of everything, but then it could have been more in depth with individual items. sometimes a charecters, places, or items only have a phrase or word to describe it. but it is still the most in depth encyclopedia you can get. . . in fact its the only one

To put it in short- the best Trekkie encyclopedia there is.

I just love those biographies on important characters.

Before I lost this, I was constantly using this as a point of reference for the time line of things and to make sure I wasn't mispelling certain things.. getting other things right, what was where, what all kinds of Star ship classes there wear, etc... this was all for a fan fiction novel that I was, am.. writing. Good thing I put some of those things I was always looking at.. on paper.. so I didn't have to lug the book around everywhere I went.

Granted it's lacking the last few seasons of Voyager and the whole of Enterprise, but I thank Okura for even making "an" edition of these, though it would be nice for a new one.

I bought this book as an additional material to study for the CISA exam. However it didn't help me with the exam at all. Furthermore, in an attempt to cover many things, it did not cover anything in detail. This book is just an endless recollection of bullet points. On top of that, it misses very sensitive topics like disaster recovery planning.

Absolutely one of the top books on my reading list. A great source of information. This is an excellent book for use in the work place or in the classroom!!! Don't pass it up if you are in or are thinking of getting into the IT Security field.

One can easily find information on IT Auditing and IT Governance (ITG) on the web. If you are passionate by the field, chances are that you are already a member of ISACA and well aware of the great value crystallized in the hundreds of articles available from its site.

But if you wish to structure your understanding and dive in just deep enough not to get lost into the specifics while always keeping a clear idea of where you stand in the vast body of knowledge, then I strongly advise you this excellent manual whose third edition reflects a very high maturity level, to use a common ITG concept.

The extensive index and table of content will guide you amongst its 21 chapters and 800+ pages. The synthesis and questions at the end of each chapter will help you focus on the essential information to be remembered from your reading, whether you are preparing for the CISA / CGEIT exams or not.

Impressed by the work done to compile such a valuable reference book and by the limpidness of its content, I give it a maximum rating. It's high price was definitely worth my investment.

Audit is not the most exciting topic in the world, but this no fluff book really sets the standard. The care the authors took is obvious from the start, the table of contents is one of the most detailed I have ever seen, it allows the book to be used as a reference.

My favorite chapter was Quality Management, best job of making quality approachable I have seen to date. My least favorite was Project Management, it seemed to lack the application and lean to theory a bit.

I am not an auditor, but as an auditee, this book really helped me understand how they think. Recommended!

This book has some material relevant to the CISA examination based on the 2003 content areas, although it is not organized or focused as a CISA examination guide. If you are looking for CISA review material for the test, I would strongly suggest to stick with ISACA's combination of review manual and questions CD. I also searched everywhere for study aids for this grueling test and ended up using ISACA's expensive material, but it proved to be the best choice as I passed the Dec 2006 test.

However, as owner of a copy of this book, I assure you that this is an excellent reference of IT management, planning, implementation, risk assessment and control procedures for anyone in the IT business. Most of the material is still relevant as of 2007.

This book was recommended by the instructor. It's a lot of book, and at times difficult to find the exact information you need. There were a lot of long-winded explanations that sometimes confused. The author is Welsh, so there are a lot of references to that culture that Americans might not understand.
On the other hand, it was helpful for correlation and regression analysis.
I bought the SPSS Survival Manual by Julie Pallant also. I ended up using it more often, as I could get to the information I needed for a particular task faster.

I find this boook to be extremely helpful. It explains the psychology statistics in a very easy to understand conversational manner. Each SPSS test is described in thourough detail with full color examples and each output box is thouroughly explained. The only thing that prevented me from giving this a perfect 5 is that the ink seems to have never completley dried. Since I handle this book a lot I am finding that the text can smudge very easily.I have to treat it with extra care or the words could easily become incomprehensible. Overall 4 and 1/2 stars.

This is an excellent book with a lot of humor, which makes reading statistics an enjoyment.Gives a lot of info for working on SPSS.

I've taken a bazillion seminars / classes in stats/spss and never have I laughed out loud like this author inspires the reader to do. I'm having a ball reading and understanding this book - now I understand why my faculty mentor loves Andy Field as a writer/teacher. This is a MUST text on your shelf.

I have looked at a number of alternatives and completely agree with an earlier reviewer: this is the best book on the subject. I relied on the second edition of this book to complete my doctoral dissertation. This wonderful book not only saved me thousands of dollars in statistical consultant's fees, but it also taught me a great deal about statistical analysis using SPSS. Even with my degree now completed, I am glad I invested in the 3rd edition of Field's textbook. The new edition's full-color pages, numerous updates and additions make learning statistics an activity one can enjoy.

The word:value ratio is poor. Compression is needed. Overly focused on collecting data, nothing penetrating is offered about using it.

Way too much detail for someone not looking to treat the Internet like rocket science :) Otherwise, book is good. Just too deep and complicated for beginners.

I love that Avinash has broken down the learning process into digestible chunks, it really is an hour a day. Add to that this man is the Chief Analytics Guru for Google and you have a winning combination. This book is a must-use for anyone who runs a website.

If you're looking to get into web analytics, this by far, is the book to pick up. I've taken the UBC web analytics program, and this book pretty much summarizes the entire program (as of the writing of this review) without all the typos, and repetition. It's straight to the point and very affordable.

You will NOT learn specific KPIs (you won't really get much of this at UBC either), but you will learn how to think like a web analyst. You also won't learn of advanced techniques, or learn how to use GA or Omniture - but it's definitely a good intro book.

Light reading, friendly tone. Definitely worth the purchase.

Quoting from this book in meetings at my company is like reading from the scriptures at bible study. Not in that it is seen as unquestionable wisdom taken on faith. Just the opposite, we have all questioned it and found it to hold true both in theory and in practice.

The best part is that each section of the book can be taken individually and applied almost the same day.

I recently bought this book from Amazon. Just finished Chapter 3. This book is full of real-life advice about designing and delivering Thread-safe classes. More importantly, it helps us (Java Developers) to question whether the 3rd party library we use in projects are thread-safe or not and spot concurrency "mousetraps".

This books introduces a topic usually with a "Bad" thread example and then reasons out the potential deficiencies (race conditions, etc.) that may happen when things go wrong with that code. Then (thankfully!) they propose a alternative correct solution in easy to understand code.

This book also addresses a gaping hole in current Javadocs standards followed by devlopers : not clearly mentioning the Thread-safety aspect of the class.

In all a excellent book and a must read along with "Effective Java".

This is definitely the best concurrency book for Java out there. It gives you pretty much all the concepts you ever need to know about concurrency in general. From basic concurrency principles to concurrency issues that would arise in almost all concurrent programs, and finally to some optimization techniques. It also provides some in-sights on some of the Java concurrent utility classes provided by the JDK package.

However, this book is not for Java beginners. You need to have an intermediate understanding of Java and some general programming/software engineering concepts. Also, if you are just starting with concurrent programming, this book might be slightly challenging at the beginning. But you should be able to pick it up fairly quickly.

And if you are already a concurrency expert or have quite some understandings about concurrency in general, this book will still solve a lot of the myths out there and may inspire you to further research on some of the topics.

Overall, this is a definite buy if you want to do concurrent programming.

This book is a must read for anyone who works in multithreaded environment. Even if you don't create threads yourself but use application server or any other environment where multiple threads execute at once, you cannot miss it. This book will tell you why and how synchronization happen - why what you think should work will not and how to read code for multithreaded application. If you never heard about Java Memory Model (JMM) you should not even touch multithreaded applications without reading this book.

Excellent and timeless work that everyone should read if you are writing Java applications because all apps are now running on multi-processor systems due to progress in Dual/Quad core chip technologies.

This is the best book on java. If you are planning on using java as a real language for development, you should read this book before you write your first interface or draw your first box on the whiteboard.

I buy this book for everyone who starts on my team. It is really that good.

I NEVER write reviews; however Mr. Troelsen for this effort has earned it. He has written by far one of the best written tech books on C programming I've ever read, and for COM/ATL this book makes writing interfaces for VB both understandable and accessible. Coverage and background is sufficient, and equally important for those who don't do this every day for a living, the depth in setting up projects in Visual Studio is also there so one unfamiliar with technical setup issues involved in setting up an ATL COM project are enabled to create their own. All I can say is well done, please keep up the good work, very much appreciated. Looking forward to your next releases.

Sincerely,
Dr. Mathew G. Pelletier, Research Engineer

This book is the perfect example of a good "Computer" book: It teaches what it needs to teach in a way you understand.
It covers all the important stuf like BSTRs, Smart Pointers, DCOM, TLBs, IDLs and other buzz-like acronyms.
I used it as an only reference for learning COM and I was doing complex COM projects within weeks. Andrew Troelsen is 'the man'!

Best regards,

Describe low level COM and then ATL internals and interfaces which can let reader easily understand such complex mechanism. Though the book is a little bit old, it can still be served as a good reference.

Apart from the fact that so many customers gave 5 stars to this book, there's another indicator of its value: it looks like nobody wants to resell it after they are done reading it. I, for one, intend to keep it for reference...

I've been programming in C# for a few years, and now I needed to learn COM. This book was the best tech manual I've ever read.

My recommendation is: if you need to learn COM, do not waste your money on any other book until you've read this one.

My current project at work required me to learn COM. I purchased several books to assist in the learning, and I must say that this book is absolutely indispensible, both as an instructional medium and as a reference. I highly recommend this book to anyone needing to learn about COM.

What's inside? It starts with a basic intro to COM, useful (dare I say it) for managers as well as the developer to get the big picture. Then it goes into a discussion of ATL and design patterns. This second section is incredibly important since ATL is for COM as STL is for C++. It finishes off with some of the more advanced areas of study in COM. Only a few advanced topics are not covered (custom marshalling for one), but considering it starts from an assumed ignorance of COM, it does reach a good level of detail.

Who am I? I studied computer science in University. However, I had never previously developped on Windows. I am primarily a C++ programmer, with some experience with Java. Knowledge of C++ (I would say more than just a familiarity) should be a prereq. to reading, but that's about it. It introduces most OO topics you need in the first chapters that most experienced developers can probably skip.

Very well written book; first time I am understanding the .Net framework!

Can't wait to read his other book that I also purchased: Windows via C/C++.

[...]

The book is very clearly written, and I typically have issues with code samples showing nuances of languages and environments, but they are quite clear here.

This was recommended reading that I did before beginning a dev job out of school since I had worked almost exclusively in a *nix environment, but would have to at least be able to read (and eventually write a bit of) managed code for the Windows CLR. It is a thorough introduction to the necessities of CLR coding and gives very useful analogies/similarities with other languages that I found quite useful (especially C++).

Without this, I would have spent a LOT of time on my own writing various test programs and not fully understanding what was going on under the covers. There is also quite a bit of code samples showing the IL generated for the runtime that is quite useful.

Other reviews cover the topics etc., and all I'll say about them is that they are all applicable and clearly written.

The book is nice, I have read 2 books written by Jeff. Most of time the author explain the C# language features which are so easy to read in MSDN. I like to read more about CLR, compared to Java, where are the places that CLR works smoothly with Windows OS, ..etc. As for language itself, Lippman Stanly's C# book explain better.

CLR via C# is an excellent look into the finer details of the .Net Framework. It is not really a book on how to program in C# per se (there are many excellent books on this subject, such as Programming Microsoft Visual C# 2005: The Base Class Library by Francesco Balena) but more a book on how to get the most out of the .Net Framework while using the C# language as your vehicle. If you are new to programming or to C#, this should probably not be your first or even second book on the subject.

In this 648 page journey through the CLR, Mr. Richter covers such subjects as how code is converted from high level C# to MSIL, Types, Generics, Events, and Asynchronous programming, to name just a few. The book assumes some level of knowledge not just of C# but of programming in general. The author does assume that you, as the reader, are familiar with some common data structures and programming best practices. Mr. Richter also interjects his own opinion at various times on why certain features work the way they do, or how they would/should work were he in charge of creating the CLR.

If you are already a competent C# or VB.Net developer who is ready to take your development skills to the next level, I highly recommend this book. At 648 pages long, it may take some time to get through, but I can guarantee it will be time well spent.

Considering how many books about .NET there are today, it's surprising how many of these books are really rather good.

However, there are a number of books that are truly GREAT. This is one of them.

Quite simply - if you're a .NET developer, you owe it to yourself to buy this book, regardless of your level of skill with this or any other technology - there are few people with the skills, background and expeirence and sheer ability to write coherently that can exceed Jeff Richter in Windows development overall, and his ability to detail just HOW the CLR and .NET FX work is unsurpassed.

Essential reading.

Occasionally, in this crummy, heartless world, someone actually gives a damn. And when they give a damn, great things happen. This book is one example of that.

H.X. Mel has written a truly great book here -- one that is based on the premise of actually caring about the reader enough to compel a want to make them understand. In this case, Mel wants the reader to understand encryption, and succeeds.

You'll find no intimidating language or anything else of the sort here. What Mel is trying to accomplish is pure understanding, by any means necessary. And he/she succeeds.

If you want to really understand encryption (and have a *GASP* fun time reading about it in the process), get this book. If you want to not understand encryption and be intimidated by impersonal, encrypted jargonizing, then buy a different book instead.

It's been very difficult for me to understand having a key that encrypts something but can't decrypt it. The math and concepts behind RSA are far from easy. I've been looking for a book that explains it to the layman. This books makes an heroic effort, in its appendix, and has gotten me farther than any other book. This book bridges general concepts to real world techniques. The book uses many creative ideas to explain these concepts.

This book is just what I needed - a quick tutorial on PKI. It is easy to read and the examples are straight forward. The book is an excellent place to start if you need to get up to speed on cryptography.

Being a technical book about a heavy topic I was pleasantly surprised that this book was pretty much "unputdownable". Concepts related to digital certificates, private key/public key cryptography, SSL protocol etc. are lucidly explained and very well presented without for a moment losing track of the overall context. All the chapters are short and sweet and cover everything essential for moving forward with confidence to the next chapter. I would highly recommend reading this book from cover to cover to anyone who is not satisfied with the half-baked knowledge available out there on this subject.

Cryptography Decrypted is an easy to read and fun book that explains how cryptography has evolved from Caesar's time to now. The author goes over how encryption is used in all areas of communication, and what sequential systems have deveoped to stop hacker attacks along the way. It is detailed but fun to read, and explains how all the enigmatic parts, like Private Keys, Public Keys, Secret Keys, Digital Signatures, SMIME, PGP, RSA, SHA-1 ect. all fit together.
This is an excellent 300 page softback that takes the mystery out of encryption and cryptanalysis. I highly recommend it.
Would love to see H.X. Mel and Doris Baker update it from 2001 to include all that has changed and been added to the present time.

This book was a fascinating autobiography of how becoming a `cyborg' made Chorost more human. A cyborg is "shorthand for cybernetic organism..., and is defined by WordNet as `a human being whose body has been taken over in whole or in part by electromechanical devices'" (7). He approached the book by explaining the human side of having a computer control one of your senses. Instead of thinking about the fact that he would be able to hear again, he was having trouble with the fact that he would not be in control of his hearing. It is a unique story detailing the process of cochlear implants, as he describes his fascination with computers, and his witty sense of humor all of which was complemented by his scientific background. It is a heart felt story that showed the life of a man adjusting to becoming a `cyborg'.

Chorost had been partially deaf his entire life relying on hearing aides to allow him to hear. The story starts off describing the tragic day of losing what little hearing he had left. He gave such distinct detail that you know exactly what he is going through. While he was thinking his hearing aide batteries were dying, he actually was going completely deaf. His hair cells are still intact and can be triggered with electrodes, which led him to be a candidate for cochlear implants. Contemplating the idea of having a computerized chip in his head was overwhelming and he gave an interesting point of view of his dilemma. To him, it was more than being able to hear again which is how most people would view cochlear implants; it was losing part of being human and being controlled by a mini computer scared him. The same kind of technology he was obsessed with was going into his body.

Throughout the book he talks about the struggles he had as a kid with his hearing problems and really explains his way of thinking. He really allows the readers to involve themselves with the story, and seems to say exactly what is on his mind about his new implant. He speaks of the foreign object in his ear and just spits out whatever thought come to his mind. It gives a vivid imagination of what he is going through and the side effects, so to speak, of a surgery of this kind. It shows the implications and hardships that have to be overcome to hear again. "The essence of the cyborgness is the presence of software that makes if-then-else decisions and acts on the body. It's the `acts' part that is important." His concern for not having control over one of his sense is a troubling matter for him. He is very skeptical about being `switched on' and when he reenters the world of hearing he feels like he is playing a guessing game in deciphering their words. The daily struggle of dealing with his new computerized hearing system was apparent.

Chorost went into detail about the anatomy of the ear and how the damage actually occurred to allow the reader to understand how the cochlear implants work. He keeps referring to being less human due to the non-control of this computerized system attached to his skull. He says sixteen electrodes are working to stimulate the neurons in the cochlea to decipher sounds control his hearing. "It was strange that I should be so stubborn about perceiving the world in one and only one way, because the exact thing I loved about computers was their infinite malleability, their ability to create worlds out of imagination "(75). After switching a few electrodes off, he was finally able to hear and distinguish sounds again like the difference between male and female sounds. "The software had not changed. The world presumably had not changed. What had to have changed was my brain" (86). He believes the brain is plastic and "when a part of a body changes, so does the area of the brain that controls it" (87).

He describes the everyday normal stuff he goes through as not being so simple and easy. For example, getting a cell phone was a large task because he has to find one that would not interfere with his processor, one that would enter a patch cable and then of course one that works in the area he resides. He even talks about the difficulty of his sex life and how that works out for him. His openness about his personal life might surprise or offend some readers, however, I loved it. This is because that is exactly how I write and would like to read a book like this. It allows for a deeper understanding of what the author is going through by learning various aspects of his life. He also goes into his longing for a group of good friends and the different ways he goes about doing it.

By adjusting to his implants, he realized they helped in more ways then he ever imagined. " The computer invaded the sacred domain of my body, yet to my own astonishment we learned to work together as a total system, mutually changing each other in the process. I fed it lithium-ion batteries; it fed me electrons. I altered its software; it repartterened the dendrites in my auditory cortex. We have literally reprogrammed each other" (156). "The one hundred and forty thousand transistors in my skull give me sound, but they cannot make me listen. Its only when I listen that my cyborg technologies make me a better human being" (183). Over the years, his hearing improved with the software updates. He attributes this improvement to neural plasticity, as his auditory cortex is completely rewired due to the increase stimulation.

I thoroughly enjoyed the writing style of this book. As a partially deaf girl, I can closely relate to the author. The way he described hearing aide batteries dying and the way it sounds when you put a new one in is exactly what goes through my mind. It was cool to see how he really spoke what was on his mind and that other people know what I go though on a regular basis. I also enjoyed his detailed description about the cochlear implants because I was never sure how they actually worked. Due to his writing style, to "just read this book" is an understatement, it's more like you experience the book. This book was provoking, and well written with a unique writing style that was an enjoyable and educational read. I would definitely recommend it to anyone that wants an extraordinary read.

Rebuilt: My Journey Back to the Hearing World

Michael Chorost does an excellent job of explaining the *human* side of cochlear implantation, offering a perspective that just understanding the mechanics does not. I found myself drawn into the book as he described his feeling of despair, as the little bit of hearing he did have mysteriously failed one day.

Chorost also provides an insightful view of life in the Signing community, and how the implant may ultimately result in its demise. While I don't agree with those who call this 'genocide', those chapters provided an interesting and thought-provoking point of view.

The book is not flawless. Sometimes the author's meanderings on life as a cyborg seem to have no clear destination in sight. But the perspectives provided more than made up for the occasional drift. As someone interested in Augmented Reality, I viewed these chapters as a sneak preview of what the next few years will bring.

I also found Chorost's discussion of his sex life to be gratuitous, by which I mean that had it been omitted, I wouldn't have finished the book saying "That was a great book; I only wish I knew more about what he did in bed." But others may find these passages make the protagonist more human. I guess that's what makes horse races.

All in all, definitely a worthwhile read if you're interested in getting beyond the electrodes and MIPs and understanding the human side of all this.

This is a very well-written book but it was very technical and dry in places. I still ordered my own copy of it since the subject matter is an important one for my family.

I have a CI too and I don't consider myself to be a cyborg or part computer. I consider myself lucky and fortunate to be in a time where this is possible. I lost my hearing suddenly before we left for a trip out west to the Rockies at the age of 34 and a young mom of twin boys that were not even two yet. Scary? Oh you betcha. I got mine for a variety of reasons but mainly because I needed to hear. Like the author of this book, I had grown up wearing hearing aids. So getting the implant was a necessity for me and one that I am eternally grateful for.

This book is very interesting in the aspect of technology and how cochlear implant works. This book would be perfect for my husband and dad to read since they love anything technical. But all the references to science fiction turned me off as well as his personal stories about his dating/sex life. I honestly don't care about that so that is why this is rated a three stars instead of a four. If they were trimmed out or modified, then this would be a four.

I really do appreciate the section on how the Deaf Culture changed from the year of 2000 to 2004 (or something like that). I did watch the movie, "Sound and the Fury" and for the first time in my life, I had a glimpse of what the Deaf Culture is about (not that I agree with it). This author went into more details (and got me to order more books on that subject) about something that has changed since I was a child. As a mother of a HOH child who may be a candidate for a CI, this book is helpful in sharing information that I may not get otherwise.

This is an interesting book and a great introduction to cochlear implants and how it affects one man's life and how it affects society today. It is a good read and a helpful one.

4/28/08

Excellent book for the hearing impaired and non-impaired alike. Much detail on living and learning to adapt in a hearing world. Highly recommended.

When I started going deaf, people often said "Well worse things can happen". That is certainly true. Deaf is not dead. But there is a connection that maybe only a poet should make, and Michael Chorost was deaf and is a poet, so he can speak with a poetic inner voice that rings true, even though I will never be able to hear anything really ring again. For now, I have not yet gotten a cochlear implant and simply struggle to hold on to my rapidly diminishing hearing by increasingly expensive and often frustrating hearing aids. Michael's story has helped me to better accept my loss: technology cannot give me back my hearing the way it was, but it can help, and I am certainly not dead. Indeed, compared to Michael and many others, I am really very lucky, since I had many long years of good hearing, and now I look forward to more years of great living even with the hearing loss. I thank Michael for helping me to gain a measured, realistic, perspective on my deafness. This is a book about living, not just about living with a disability.