Klemens, 21st Century C (2nd ed., O’Reilly, 2014)

As everyone knows, Mark Twain defined a classic as a book that everyone wants to have read and no one wants to read. Everybody who does some programming knows that K&R is a classic, by any standard– it’s the Rosetta stone of modern C programming, but it also helps to clarify the design principles (and of course the syntax) of many of the modern programming languages that are derived from C. Even beyond languages with a clear C lineage, it’s easy to see the way that a whole host of other modern programming languages have been written to simplify things that are tedious or risky in C. At the same time– and like a lot of other people, I’d imagine– K&R sits on my shelf and stares at me most of the time. When I open it, sometimes I think “What an impressively written book! What concision and clarity!” Most of the time, though, I think, “Wow, how gnarly– thank God for Python!”; or I wonder whether any of the details K&R fuss over are relevant today.

Ben Klemens’ 21st Century C is intended to resolve some of this shock, and to serve as an introduction to modern ways of working in C. The first part of the book presents tools and best practices for this (including debugging, testing, and version control), while the second half discusses how to write modern C– C in a world where, among other things, the rigid memory constraints taken for granted in K&R no longer apply. Some parts of the book (like the discussion of pointers) are clearly meant as an introduction or refresher for readers who aren’t comfortable in C, and the book includes a handy appendix on the basics of C. Other parts live up to the book’s billing as an explanation of what has changed in the world of C. The discussion of new structures in modern C, for example, is a highlight of the book. Klemens’ discussion of string handling in Chapter 9 was also interesting, though briefer than it might have been. (Perhaps with good reason: as someone who works almost exclusively with strings– and even though Unicode in modern languages isn’t always fun, either– I remain unconvinced that working with strings in C is something I want to do on a regular basis.)

As my comments above suggest, I am not an experienced C programmer (despite the occasional stab at the exercises in K&R), and am thus rather unqualified to pass judgment on the soundness of any of Klemens’ code. I can only assume that the infelicities and problems mentioned in reviews of the first edition of the work have been resolved. As a C tyro, though, I felt that Klemens effectively explains the ways that different practices– and the C standards, as well– have evolved over the years. It would be tempting, I think, for the book to remain at the level of vague generalities, but the book strikes a nice balance between high-level discussion of the way C programming has changed over the years and detailed discussion of what’s going on under the hood. It helps immensely, I think, that Klemens has a light, humorous touch– he notes that the manual memory model “is why Jesus weeps when he has to code in C”– and the humorous asides help to leaven some of the necessarily technical passages of the book.

Klemens’ book has the unenviable task of competing with K&R, and there are parts where 21st Century C suffers for the comparison. I still prefer K&R’s discussion of pointers; and I felt that there were a handful of sections that add little to what’s already in K&R. Klemens is fond of comparing C to punk rock, and upon reflection, I believe the comparison is an apt one. To push the metaphor further, there are ways in which K&R is, like a classic punk album, indelible in its simplicity and directness. To my mind, Klemens’ book is a worthy attempt to take that simplicity and directness and make it speak to a changed world. Klemens’ book isn’t perfect; if we’re honest with ourselves, though, even the hardiest classics aren’t always, either.