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Ask HN: Learning C

62 pointsFiveFiftyOne65 comments

Throughout my career, I've viewed C as the sleeping monster that mere mortals such as myself dare not waken. However, as I increasingly seek to achieve more complex goals in my projects, I find myself encountering C libraries (such as GMime) which will answer all my questions, if I could actually program in C. I have a copy of C Primer Plus Fifth Edition at hand, a development FreeBSD server as well as my Mac, but would like to ask of this community if they are aware of any other references, such as old CS course materials, which may help. Many thanks in advance. I realise that this is a long term goal, but feel that with my taste in server platform and operations software, C will prove a boon to me.

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Just about everybody who answers this will say that K&R is good, and I agree, but in addition to this I found that learning the basics of assembly was helpful. You can really see what's going on with the stack, what a pointer really is (pointers are really the only tough part about learning C, everything else will be the same old same old if you already know how to program), and the difference between a system call and a regular function call, and it doesn't take much time to learn.

Books by W. Richard Stevens were old when I was learning, and older now, but they were the best guides to taking it to the next levels. You can pick up a lot of tricks and stylistic pointers from him while learning about UNIX features and networking. Maybe somebody will chime in with a more up-to-date resource that does the same thing.

I'd second this. In fact, Steve Yegge once said this about K&R ( http://steve.yegge.googlepages.com/ten-great-books ):

This is an odd little book. It's frequently mistaken for an introductory programming book, which inevitably leads to frustration. It's not a good way to learn how to program; it expects that you're already familiar with machine architecture, assembly language, compilers, and at least one other high-level language.

It's not even a very good way to learn C. The idioms and best-practices for C programming have evolved substantially, even since the second edition was published, and some of the code samples look a bit dated.

As the parent said, you'll appreciate C only if you learn about machine architecture and Unix. Diving into a large codebase will get you acquainted with "modern" C.

I've found the book C Traps and Pitfalls to be the book to get you to think like a C programmer. The C Puzzle Book is pretty good for exercises, and Expert C Programming does a good job exposing the ugly side of C.

I know the plural of anecdote is not data, but my personal experience was the opposite. C was the first programming I learned and I learned it by reading K&R in high school. I certainly didn't know anything about assembly, compilers, or another high-level language.

From there I learned by contributing to open source projects.

Not saying K&R is the best way, but it's not so opaque that a beginner with zero knowledge of C (or even programming) can't pick it up and learn if they're motivated to learn it.

K&R was the only C book that ever allowed me to pierce the veil of mystery surrounding C and understand it. I'd tried at least a half dozen other books and was either bored out of my mind at the painfully slow pace, or utterly baffled around chapter 2 or 3 where it leapt into pointers and seemed to just assume it was obvious.

For whatever reason K&R was a perfect storm of comprehension for me, and I came away actually knowing how to read and even sort of write C (and knowing how to search the Internet, pre-Google, or ask reasonably smart questions on the mailing list or IRC channel of the software I was working with, for answers to the harder questions). I failed miserably with every other book on the subject.

C Traps and Pitfalls: http://www.literateprogramming.com/ctraps.pdf

If you enjoyed reading those 29 pages, you might find the entire book a decent read as well: http://www.amazon.com/C-Traps-Pitfalls-Andrew-Koenig/dp/0201...

Agreed. I was scared of C for a long time, but it's actually a beautiful language. Deitel & Deitel's 'C; How to program' is a fine tutorial in both C and structured programming. YMMV.

C Programming Notes by Steve Summit should also help you get through the K&R, http://www.eskimo.com/~scs/cclass/notes/top.html; although, you'll probably get the most benefit from doing the problems/examples from K&R.

I found that learning the basics of assembly was helpful. You can really see what's going on with the stack, what a pointer really is (pointers are really the only tough part about learning C, everything else will be the same old same old if you already know how to program)

This is key advice. Understand hardware first and pointers are obvious, don't and they are (apparently) confounding.

what do you recommend for understanding assembly?

I used a book called "Programming From the Ground Up," which is not comprehensive but it teaches you the basics, which is really all you need for this purpose. It's online somewhere.

C isn't hard, don't worry! It's actually a fairly simple language. But it's medium/low-level and there is a lot of power within its simplicity. Fast to learn, but a long time to master, as one might say.

I don't know what people are using to learn C these days, but the standard has always been the white book http://www.amazon.com/Programming-Language-Prentice-Hall-Sof...

You will find yourself spending more time thinking about programming concepts rather than dealing with C syntax, since it's pretty concise. I don't know how difficult it is to learn about pointers if you have already been programming for a while but haven't had to use references directly, but it's very important to learn. C does not do too much for you on its own, so handling references yourself is an important skill. It will also help you understand how higher level languages and concepts work.

If you are working through it and find that you're enjoying yourself, congratulations, you're a programmer :] Then it's time to pick up the 1st volume of Knuth and start working through that.

Indeed, the problem with C is just that. Once you understand how it works, you'll realize it's just a thin abstraction layer over assembly language. It really is just that simple. My last job was almost purely C, and what made C "scary" at times were:

1. naming conventions. I don't know why C programmers use the strange names that they do.

2. macros. C macros are a pain to read and follow.

I hope things will be easier to learn if you know this going in, because that's really all there is to it.

The catch with C is that while it is simple, writing good code with it is not. You have two tools for metaprogramming: macros and function pointers. C++ classes seem evil, until you see what people do in C in the absense of any mechanism for polymorphism.

Thankfully for you, you probably will only ever need to deal with libraries, not applications, so you'll never have to deal with the hell that comes with trying to use C for higher level work.

They use the strange names that they do because a function declared in C is declared everywhere in the whole program. They use strange names to try to stay out of your way; i. e. it would be really bad if two functions had the same name.

You're right that C's lack of namespaces makes for funky names. However, note that "static" functions are visible only within their compilation unit, which can bring some order to the madness.

Yes, exactly. And yet people continued to use the unhelpful, oblique prefixes and suffixes they used for global symbols nonetheless.

Best beginner text after K&R is Kelly and Pohl's "A Book on C"; very newbie friendly and at the same time uses traditional C examples (i.e. memory management, serializing and reading-back record-oriented data stored in structs, file and directory manipulation, string manipulation, etc.)

Most other C books will just treat it as a stepping stone for C++ which is a different beast, and a few awful offenders will stretch it to Java!

To see a few Algorithm implementations in C, there is no better friend than Robert Sedgwich's polyglot tome; it's the applied Knuth volumes that everyone keeps on their desk (quickly swapped for the actual Knuth volumes when expecting hacker guests.)

Along with C materials you will also need Unix materials. The two are inseparable and fuel each other. You already have a decent Unix in your Mac, and your FreeBSD is the best of the Unix breed bearing the original blood. For that there are no better companions than the books by Richard Stevens, both for system and network programming.

For larger scale software engineering you will need a few small to mid projects of your own. You will deal with header file and Make dependency problems, a few unix and processor portability problems and a few other stuff. The solution to those problems along with a fat library of useful routines are found in "C Interfaces and Implementations" by Hanson. It's a literate programming text where source code is interwoven with prose documentation and it's very self evident.

Along with productive C programming you might need to look into the darker side of C and Unix and follow the papers of the hacking underground (yes, HACKING, dispute the terminology all you want, but I think some blackhats deserve the noble noun more than javascript and CSS jockeys.) Unix and C have plenty of Not-TODOs to motivate plenty of caution. Hoglun and McGraw's Exploiting Software is the canonical C-Do-Not text books.

If you want to read library source code, your FreeBSD source code should give you plenty to keep you busy. Start with the sources for the games; I spent an enjoyable summer porting Minix games to DOS and taught me allot. There is also "The Standard Function Library", or SFL, google it, it has the cleanest C sources you ever seen. Highly recommended.

And should you ever want to write a C compiler, like I attempted, here is some advice: implement Oberon instead. Everything you could possibly learn at 1/100th of the headache.

Just the 2 cents of a guy who will only write C code again if there was a gun to his head ;-)

I actually picked up and then put down a good looking book on Unix systems programming either by Stevens, or by someone who worked very closely with him and wrote an updated version. I think I'll scream off to the book store and track it down.

It's the updated version of APUE done by Rago (the guy who did Unix System V Network Programming; a fairly good book but with a narrow and almost obselete focus; sysv STREAMS -- a very good idea whose time hasn't come.)

> Best beginner text after K&R is Kelly and Pohl's "A Book on C";

That's the book I used to teach myself C and I though it was just brilliant.

You should absolutely learn C. A good knowledge of C is a very valuable asset for all sorts of work, especially on Unix.

Thankfully, C is straightforward to learn. The major concept you need to understand is pointers; once you've done that, there are some syntactic oddities to absorb (typedefs, function pointer syntax, arrays vs. pointers), and you should skim through the standard library (which is tiny compared to Java, or even C++), and you're most of the way there.

In addition to K&R, I've hears that Steele and Harbison's "C: A Reference Manual" is very good, although I haven't read it personally.

I have Steele and Harbison's "C: A Reference Manual", and _is_ very good, but probably not for _learning_ C. It does have very good explanations of some under-the-hood things that I haven't found elsewhere. It is also a good reference on the C std library, and does a good job at pointing out possible incompatibilities between ISO C, `traditional' C, and vendor-specific dialects. One of the things that I have always found confusing about C is that code can be written in several ways, depending on how lax the compiler is about enforcing different versions of the C standard.

A great resource I have enjoyed while brushing up my C skills has been CS107 at Stanford University on the web.

http://www.stanford.edu/class/cs107/

You can find the lectures on academicearth.org, or on iTunesU if you prefer to download them that way.

Jerry Cain is a great lecturer. I wish they'd post the assignments with the files they provide the students though. Maybe someday.

Yes. CS107 is the class that made C and assembly finally click for me. I have access to the assignment files; email me (in my profile) if you want them.

FYI, CS107 has changed considerably this year, so the course description on the current course site is a bit different from what you'll find on Academic Earth.

http://academicearth.org/courses/programming-paradigms

First, congratulations. You're making the right decision. Programmers who are ignorant of C leave certain roles and problem domains closed off to them. Even if your primary language is something else, not being afraid to roll up your sleeves and fix performance and correctness problems in the compilers and runtimes themselves makes you more valuable, more confident, and better able to reason about how the runtime will map your input to the machine. And proficiency with system-building languages and tools is a prerequisite if you ever aspire to be a "head surgeon," "10x programmer", "ninja", or whatever the heck the kids are calling it these days :).

K&R et al. are fine, but I'm a particular fan of two slightly oddball, but great, books about C:

1. van der Linden's Deep C Secrets. Short of implementing a C compiler yourself, reading this book is the surest path to completely understanding some aspects of the C linkage model, and the distinction between arrays and pointers. It's also entertainingly written, which always helps.

2. The Lions Book, an annotated source listing for the Unix v6 kernel. The subject matter is one of the most beautiful and influential programs ever written. This ~10k-line program is completely understandable in six weeks' study, a couple months' tops, yet it staked out almost all of the abstractions that still underly modern operating systems. It is also C's native environment: C was literally invented to write this program. And while it's dated in some of its peculiarities ("=+" where we'd write "+=", identifiers only being significant in the first 8 characters, no typedef yet, a lot more reliance on the register keyword, etc.), it's damned fine code, by any standard. Each page brims over with good, informed engineering trade-offs; the sweet spot may have shifted since the days of 128k core and 16-bit CPUs, but the thinking that goes into those trade-offs is mostly unchanged.

This falls more into the "tips and tricks" category, but I wish someone had mentioned this to me earlier. Once you have a good book on C[1] install all the man pages for the standard library. Once you start writing code, being able to say something like "man strlen" is amazingly useful.

I made the most progress in C when I took a class on OSs. Mainly, we wrote systems programming sorts of things like a simple shell, our own version of malloc, a simple user-space thread library, and so on. This really gave me insight into how these things would be done for real. Also, writing something really linked-list-heavy gets you a feel for pointers really quickly.

[1]: I have K&R ANSI C and I found it very concise and well-written. It is probably one step up from the "raw newbie" class of books in terms of difficulty, but should feel just right for someone already acquainted with (an) other language(s).

You should learn C. It is a small language but to master it requires a lot of work for a reason: you need to get good at design. When all you have in your hands are structures and pointers you absolutely need to develop the ability to design well organized programs in different layers of abstractions, otherwise to scale over the 1000 lines of code program is almost impossible. This is probably the most valuable thing C will teach to you.

1. In Which I Join The Choir

You should definitely learn C:

* You'll learn the memory hierarchy, which is probably the most important thing to know about performant software.

* You'll get 100x better at debugging --- both because you'll have practice, and because most of the tools you use to debug C code work for higher-level languages (gdb is still a better Ruby debugger than Ruby's own debugger).

* You'll be able to bridge Python (or Perl) to almost any library or framework you ever need.

2. In Which I Express Reservations

Don't learn assembly. In my (C and assembly-heavy) career, I've found it works in exactly the opposite direction: you won't really understand assembly until you understand C code. There are mainstream architectures (SPARC and MIPS) that are literally designed as drivers for C compilers.

You'll eventually want to be conversant in assembly so that you can debug faster (when it comes to the runtime, the C language is a flimsy abstraction indeed). But you should let your needs and interests drag you into the machine, just like you should probably learn "Stairway" and "Smoke On The Water" before mastering barre chords and sight reading --- you can have a pretty excellent punk band without ever knowing how to read music.

3. There Are Books

Everyone is going to have an opinion about K&R. What I think you need to know is, it's short and it's dry. I re-read it 6 years into my career and I was surprised at how rich it was; there's a lot of design and data structures material, beyond the core language.

There's a C book that changed my life. It's David Hanson's "C Interfaces And Implementations" (CII). I will now make a case for why it's the first and only book you'll need. You're coming to C from a high-level language. That language is giving you a couple key things you don't realize you depend on:

* Garbage collection

* Lists and hash tables

* Resizeable strings

Almost every major C project contains a site-specific reimplementation of these concepts. CII gives you one --- an internally consistent one, relatively well implemented, and extremely well documented. In doing so, it also teaches you the single most important thing about writing good C programs, which is how to build abstractions around your gnarly code.

The difference between people who know C as a language and people who can actually deliver software in it is resizeable containers (linked lists, dynamic memory allocation, high-level strings, doesn't really matter what the specific is).

The other book you want is "Advanced Programming In The Unix Environment" (or its moral equivalent, "Win32 Programming").

CII is "how". APUE is "what".

Finally, I like (for new programmers) "The Practice Of Programming".

4. What I Did To Get Started

I "knew" C for a while (maybe since I was 13) before I actually started coding in it. Two things got me unstuck.

First, I picked a couple basic Unix APIs and wrote little toy programs around them. If I remember correctly, the first thing I wrote was "who", from "getpwnam(3)", which forced me to do some basic strings and structure pointers.

Second, I wrote network code from a socket tutorial. Sockets are a great thing to get started on; just write a scraper for a service you like, and there's a zillion little problems you'll have to solve that are the same problems you solve in every other program you write.

I violently disagree with not learning assembly. Absolutely learn assembly. Just pick anything else other than x86 assembly. After learning the basics of assembly you will never have any trouble understanding pointers or any of the "hard" concepts in C.

x86 is a convoluted horror. A lot of it makes no sense except in the context of backwards compatibility, which the documentation won't necessarily point out. I highly recommend picking up a microcontroller to learn on instead of a microprocessor. Microcontrollers are mostly self-contained systems, while microprocessors are just a small piece of the picture and have complicated interfaces to the rest of the system components.

I recommend picking something in the Freescale 68HC* family. The addressing modes and instruction set are fairly clean and the architecture is simple. Something based on ARM would probably also be straightforward to learn. Don't worry about choosing a 32 bit chip, 8 or 16 bit is fine. 8 and 16 bit chips are typically simpler and will still teach you the important concepts.

Spend a couple of weeks on this and your understanding of C will be easier to come by and more thorough.

I'd steer away from the really small microcontrollers, as they tend to be register-starved (and/or memory-starved!) enough that you have to make ugly compromises, particularly in the area of call stacks. :(

ARM, PowerPC, and MIPS are all good choices if you've got appropriate hardware to play with. All three are nice, clean RISC architectures with plenty of registers and sane addressing modes.

Or try your luck at Core Wars. There you write programs in a simple assembler (Red Code) to fight against each other i.e. make your opponents execute an illegal op-code.

1. K&R - an absolute essential. I found myself in your shoes about two years ago, picked this up, and worked through it.

2. "The Unix Programming Environment" (http://www.amazon.com/Unix-Programming-Environment-Prentice-...) This is a recent find, but covers more application. It's almost a Part 2 of K&R and covers building problems and the Unix signal and file APIs. The examples are in an ancient syntax, but part of the fun is coding them and getting them to compile.

3. "The C Puzzle Book" (http://www.amazon.com/Puzzle-Book-Alan-R-Feuer/dp/0201604612) I found this one day at Fry's, and it's fucking awesome. You can effectively learn C using it without a compiler.

Good luck!

K&R http://en.wikipedia.org/wiki/The_C_Programming_Language_(boo...

I taught myself C/C++ when I was around 13. I already knew most of the concepts through my experience with Pascal, including pointers, which are harder to use than to understand. What I did have trouble with was Windows as I just couldn't figure out the API. What solved it for me was one of those old 'Game Developers' series of beginner's books. It gave detailed instructions on for a 'hello world' Windows application. After that, it was pretty easy to get the hang of it.

I don't use C much anymore (haven't since Highschool.) When I do, it's with GCC and I and the environment is still the hardest part.

Moral of the story being that C is pretty easy. I learned it with some very basic references. The hard part, supposedly, is pointers, and those are much harder to use than to understand. Basically, everything is done through them, without the usual abstractions that you would get with say, Java. You mainly just have to make sure you always have the right number of asterisks and ampersands.

One book I can suggest is Advanced Programming in the UNIX Environment by W. Richard Stevens, (revised version) which gives a very through introduction to UNIX from a C perspective. C is interesting in that it is almost a different language depending on which system you write it on and you'll spend more time learning system calls and UNIX paradigms than C syntax and pointers.

I learned C a while back, and don't regret the time spent doing so at all. This is how I'd recommend going about it:

* Everyone is going to recommend K&R, which is fine. Find a copy of C Interfaces and Implementations as well--very good implementations with explanations of standard high-level structures.

* Read source. SQLite's source, for example, is very well written and documented, and they actually have a version to download recommended for reading (everything is in one file).

* Implement. You're going to want to try implement standard Unix commands yourself. Try writing an interpreter/compiler as well. These things give you a good grip on a wide variety of C basics and will make sure you can work well with memory management and all that.

* Assembly. This is where I would learn assembly (i.e., where I did). I don't think you need to go too far in depth, but a basic working knowledge will make debugging much, much easier.

Hi avinashv, I'm interested to learn SQLite. I noticed you mention that there is a "recommended for reading" version of SQLite. Would you mind pointing out where I can find it? I browsed the website and haven't had any luck to find such information. Thanks!

It's just the "amalgamation" version off http://www.sqlite.org/download.html (it's the first download link).

Thanks!

The source for Lua is good too, as is the core userland for the various BSDs.

Chances are you already know C, but don't realize it. Java and PHP have mostly C syntax. All you have to do is substract objects and add pointers.

Like rsheridan6 said, assembly helps. It's not necessary though, as long as you realize a pointer is actually a memory address and not something abstract like a reference in Java or PHP.

... and figure out how to deal with allocating and freeing things. Taken together, pointers, and manual memory management are a big chunk to bite off. The syntax isn't the problem, in other words.

For sake of argument: How often is the syntax the primary problem in learning a new language?

The examples that come to mind are Forth and APL/K/J (all of which I've only dabbled in), but the reason they have such unconventional syntaxes is because they're conceptually very different.

And yet, because of the syntax I don't remember learning PHP. It was pretty much one night of reading the manual to get to know the API, and that was it. They're close conceptually too, not just in syntax.

If you've got the time, I highly recommend taking CS107 at Stanford (for free): http://see.stanford.edu/see/courseinfo.aspx?coll=2d712634-2b....

I became incredibly comfortable with C -- memory management, handling pointers, having a very clear picture of how types are represented in memory -- after taking that course. The lecturer (Jerry Cain) is fantastic as well.

The course changed this year so I don't have any thoughts on the current CS107 offering if you plan on taking it through their online course offerings for pay. The lectures, syllabus, and materials on Stanford Engineering Everywhere (OpenCourseWare at Stanford) are all from the course I took two years ago.

C Primer Plus was completely useless to me. As I mentioned in another thread, I tried several books on C before K&R and none of them "took". I knew (by some definition of "knew") other languages (several BASIC variants, Pascal, REXX, Amiga shell, a little 6502 and 68000 assembler, etc.) when I started learning C...but it took years, and several failed attempts before I was actually able to make sense of real C code.

My book recommendations would be K&R, Advanced Programming in the UNIX Environment by Stevens, and C: A Reference Manual by Harbison and Steele. In that order. With liberal doses of web research and reading real world examples and experimentation.

Learn C at Harvard (virtually) for free:

http://tinyapps.org/weblog/misc/200904120715_learn_c_for_fre...

Here is what worked for me.

Work through, in order, (1) K & R (2) C interfaces and Implementations by David Hanson (3) Deep C Secrets by Peter Van der Linden (4) Advanced Programming in the Unix environment

Good Luck!

I've only found two books on C worth the money. One is K&R, the other one (which I haven't seen mentioned here) is "The Standard C Library" by P.J. Plauger. It not only presents the ISO standard for the library, but Plauger's commentary on the standard, how to implement the standard C library, along with his implementation. It explains some of the murkier aspects of the C library, along with how to go about writing portable code.

If you can program well in C, everything else seems like both a blessing and a compromise.

While K&R is great, my copy is far less used than Pointers on C by Ken Reek. If you can find a cheap copy I highly recommend it. If you are working through K&R make sure to do each of the sample problems. The text is just the support to let you figure out how to do them.

I also wanted to learn C, not to learn specifics of the language per se, but to better understand the C/UNIX ecosystem. The book I chose to follow was Computer Systems: A Programmers Perspective. You can get a draft at: http://lsec.cc.ac.cn/~tcui/download/draft.pdf .

This course website from the University of Maryland has a very good introduction to C.

http://www.cs.umd.edu/class/fall2005/cmsc212/

It starts off with the fundamentals then gets into some more advanced principles. In particular, check out the "Jan Plane's Lecture Outlines" link.

Stanford's CS Ed library (particularly Nick Parlante's linked list and binary tree problem sets) is a fantastic resource for understanding the C language, it is the way i learned it.

http://cslibrary.stanford.edu/

Well, copies of K&R and C Puzzle Book are on their way, with CII and Advanced Programming In The Unix Environment (2ed) wishlisted for later. Can't find a copy of Deep C Secrets on our local Amazon equivalent, but I'll keep searching.

It may not be what you are looking for, but if you want a C based intro CS text, this classic is now freely available.

Foundations of Computer Science

http://infolab.stanford.edu/~ullman/focs.html1

Some helpful reminders for learning any programming language, http://c2.com/cgi/wiki?LearningProgrammingLanguages.

I bought K&R but in the end found http://www.cs.cf.ac.uk/Dave/C/ to be much more useful and accessible - and free!

Sure! Knowing C can definitely help with your overall understanding of how things work. It's especially helpful when learning new languages.

I uploaded a copy of K&R ANSI C for you. In my opinion, it's probably the best way to learn it.

http://whitepaperclip.com/files/ansi_c.pdf

Have fun!

This book have copyright and you can buy it in libraries.

What makes you think he's not?

Is this book free now? If not, you should kill that link.

Unfortunately K&R is all-rights-reserved copyright by Bell Labs, so this is illegal. It's also a bit ironic that you have this at the bottom of your own website:

    © 2005-2009 White Paper Clip, Inc.
    All Rights Reserved. Stealing leads to beatings.

amazon booklist I used to teach myself

http://www.amazon.com/Master-C-Programming/lm/9PUKX2J9RNUO

Brilliant. Thank you all.

I will be trying this myself, from what I can see it would be very helpful for learning C:

http://bellard.org/tcc/

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