The standard C Library shows you how to use all the library functions mandated by the ANSI and ISO Standards for the programming language C. To help you understand how to use the library, this book also shows you how to implement it. You see approximately 9,000 lines of tested, working code that is highly portable across diverse computer architectures.
Phillip James Plauger is an author and entrepreneur. He has written and co-written articles and books about programming style, software tools, the C programming language, and science fiction short stories.
Readers of comp.lang.c will be familiar with Plauger, a ubiquitous face on various ANSI/ISO standardization committees. He's put together a detailed tour of the C standard library, useful to users thereof but especially implementors. Thorough coverage of stdio is appreciated, while rather cursory treatment of the math elements is regrettable -- then again, very few people, I'm-serious-to-God-here, *very* few people -- ought be writing mathematical core code, especially in this age of appalling mathematical illiteracy among programmers. Unfortunately, ISO C99 is not (in the most recent edition I know of) covered: C90 is the basis of discussion (no such book, to the best of my knowledge, addresses C99, but the groin-grabbingly sweet C Interfaces and Implementations uses it throughout).
After the C "BIBLE" (K&R book), this is the next best book to get if you find yourself doing C programming. Though C may be a bit out of date these days, if you find yourself in its boundary for anything, then this book is an excellent resource.
Why would C be used still? Probably most likely on low memory embedded systems. This book explains and gives implementation for the entire standard C library. So if you can't afford to package the whole standard C library in your embedded system, you can use this book's implementations to help you code your own versions of the functions you need.
This book was a big time saver when I was working with embedded systems programming.
I can't think of a better way to get more acquainted with the C standard library and all of its quirks and pitfalls than by reading this book. It's basically an annotated implementation, and spends a lot of time discussing the C standard and why things are the way they are.