The Symbian OS (Symbian Books), страница 2

My goal in writing it has been to try to make Symbian OS moreaccessible to a wider audience than has been catered for to date. I hopethere is nothing dumbed-down about this book, but at the same timeI have tried to make it accessible to those who are interested, but notexpert, in the topics it covers, as well as useful to a more hands-ondeveloper audience.As Symbian OS becomes more mainstream – a volume product andnot just a niche one – I hope this book will serve as a primer for thecurious and a way in to a deeper understanding of what Symbian OS is,where it came from and why it is currently riding high.Certainly there is material here which is useful to Symbian OS developers – both seasoned and novice – and which has previously been hardto find.

However, this book takes a different approach to that of mostSymbian Press books; it is not so much a ‘how to’ book as a ‘what andwhy’ book (and to some extent also a ‘who and when’ book).Part 1 is a Symbian OS primer, a rapid introduction that sketchesthe background of the mobile telephony market, traces the emergence ofSymbian OS and Symbian the company, conducts a rapid tour of the architecture of Symbian OS, and provides a refresher – or introduction – to thekey ideas of object orientation (OO) in software.Part 2 begins the more detailed exploration of the architecture ofSymbian OS, following the Symbian OS System Model layering to providea complete, high-level, architectural description of Symbian OS.Part 3 returns to the historical approach of the primer chapters, andpresents five case studies, each exploring some aspect of Symbian OS, orof its history and evolution, in depth.

Drawing on the insights – and thexxINTRODUCTIONrecollections – of those who were involved, these studies trace and try tounderstand the forces that have shaped the operating system.Appendix A contains a component by component reference, orderedalphabetically by component name, which is definitely intended for adeveloper audience. It also includes a color pull-out of the System Modelfor the current public release, Symbian OS v9.3.Who This Book Is ForThis book is for anyone who wants to understand Symbian OS better – what Symbian OS is, why it is what it is, and how it got to be thatway. If you work with Symbian OS, or intend to, this book is for you.

Ifyou want to get under the skin of the OS and understand it more deeply,this book is very definitely for you. This book is for you too if you areinterested in the software or mobile phone industries more generally, orin the perennial themes of software development, or are merely curiousabout how real systems get made and evolve.A reasonable degree of software technical literacy is assumed, but notso much that the more casual reader should shy away. There are noexercises.

And there is no sample code.How to Use This BookThis book calls itself a sourcebook and it is intended to be used both as aprimer and as a reference. Its different sections are useful in their differentways as reference material. Both Part 1 and Part 3 are structured as astraight-through read and, I hope, they offer a good starting point fromwhich to come to Symbian OS for the first time. The material in Part 2is probably deeper than a non-developer audience needs. And while thisis not (strictly) a programming book, I hope that Symbian OS developersfind its reference material useful, or better.Telling StoriesSomeone else wrote the phrase before I did: ‘‘In every great softwareproduct is a great story’’ [McCarthy 1995]. I think it’s true.

So whilethis book is aimed at a technically aware audience, it is not addressedexclusively to an audience of programmers. I hope programmers and,more generally, software developers, designers and architects will find ituseful, especially those coming new to the OS and trying to understandit. But I hope it will be just as useful to academics and students,marketeers, technical decision makers and managers seeking to evaluateINTRODUCTIONxxiand understand Symbian OS, and indeed anyone else who is broadly inthe business of software or phones or who is just interested in such things,and who is encountering Symbian OS (or its close competitors) for thefirst time and needs to understand it. Speaking personally, I have longbeen something of an operating system junkie; to some extent, therefore,this book attempts to scratch that itch.

(You can’t work for an operatingsystem company and not have a bit of the operating system junkie in you.)I hope that understanding the deeper story behind Symbian OS willhelp those who want to (or have to) work with it to understand it betterand more deeply. Above all, I hope it will help them work better withSymbian OS than would be the case without this book.I have another purpose too. One of the things which appealed to memost in my early days in the company (which became Symbian a fewmonths after I joined) was the degree to which everyone involved increating the system shared the sense that making software is a visionaryactivity and that making good software, indeed the best possible software, is as much a moral imperative as a business one.

For an activitywhich likes to count itself as a branch of engineering, the number, andvariety, of value words which cropped up in any daily conversationcould be surprising. Making software, which is to say making this software in particular, is value-laden. ‘Delight’, ‘elegance’, ‘trust’, ‘integrity’,‘robustness’, ‘reliability’, ‘economy’ and ‘parsimony’ were all among thecompany buzzwords and very much part of the fabric of the effort, andgive a flavor of those times.

Above all, to be part of the effort to createSymbian OS was to be part of the revolution, no less. The truly personal,individual, pocketable, always-on, human-scaled device you could trustyour data to, and to some extent therefore also your identity, and yourheart as well as your head, was not yet the commonplace thing which themobile phone revolution has made of it.

Symbian – the operating systemand the company – has played its part, too, in that revolution.Symbian is currently riding high. Symbian OS has done more than finda niche; it has found (and, indeed, it has founded) a global market and hasled that market from its inception. To make that point more concretely,consider this: when I was starting work on this book, I drafted a paragraphabout 2005 being a watershed year for Symbian OS, potentially itsbreakout year.

Between then and now, as I write this at the end of 2006,the number of shipped Symbian OS phones has doubled from 50 millionto 100 million, and counting.Way back when, the company was a company of individuals – whocould be opiniated, strident and arrogant but could just as quickly switchto humility in the face of a powerful intellectual argument. Inevitably,some of that individuality has been lost with success and growth.

I hopethat by capturing some of the flavor of those times, that particular flamecan be kept burning.xxiiINTRODUCTIONI have been mindful both of commercial and personal confidencesand I believe that nothing I have written (or quoted) breaches either.(Any instances of ‘Don’t quote me!’ which appear in the text have beencarefully approved.)I have tried everywhere to observe the mantra ‘Tell no lies’, whichis not always the case in books such as this, and which here and therehas not been easy. Let me quote Bjarne Stroustrup as one inspiration forhonesty, ‘I abhor revisionist history and try to avoid it’.1 I have done mybest to follow that example.Getting Symbian OSAnyone, anywhere, can download Symbian OS in a form in which theycan learn to program it, work with it, explore it and experiment with it.Anyone can learn to write Symbian OS applications: development kitsare free, and easily available, for UIQ and S60 platforms; developmenttools (GCC and Eclipse) are free; the Symbian Press programming booksare widely available; and the possible languages range from OPL (whichbegan life as the Psion Organiser Language and is now an open-source,rapid application development language for phones based on SymbianOS) and Visual Basic (available from AppForge), through Java and Python,to full-on native Symbian OS C++.