Open-source interactive C tutorial in the browser
53 comments
·April 27, 2025herewulf
Narishma
> I was seriously hampered by the fact that this compiler couldn't produce text mode executables (any call to printf opened its own new window that definitely wasn't cmd.exe) and it couldn't set the graphics mode for blitting pixels.
This is incorrect. Visual C++ definitely could do all those things, it was in no way a toy. You probably had it mis-configured somehow.
codr7
I stole my copy of Borland C++ from school.
But as mesmerized as I was by C++ at the time, Borland Pascal was a lot more fun to play around with. I remember unsuccessfully trying to wrap my head around the different kinds of pointers, and the humble beginnings of std.
kasajian
Even the first of Visual C++ was a professional C/C++ compiler. That's been the same Microsoft compiler they've been selling for years for $500. The previous version was just called Microsoft C/C++ 7.0.
It wasn't in any way a "toy". What I think you're talking about is that Microsoft was pushing the "Visual" aspect of the IDE that it was trying to copy from Visual Basic, but with MFC, and was doing a sucky job at it. You didn't have to use it. Most of us didn't.
Buttons840
Same here. Highschool programming class was a lot of fun, learning all the basics for the first time, but I too thought the first step of being a programmer was to obtain a Microsoft product.
auselen
Probably same years… whenever we got a new computer I was removing OS shipped and installing a previous MS OS. Win3.1? Nah I want DOS, win95 nah… I want 3.1. That’s where my tools were.
Funny thing I still use win10.
giordanol
funny how much the tools you first get comfortable with shape everything after. even today, setting up a simple clean c environment is way harder than it should be for beginners. tutorials like this help, but eventually pointing people toward gcc or clang early on makes a huge difference long term.
auselen
I totally see what you mean but after 30 years of experience, I couldn’t put it that way. Even the simplest editor and a command line was enough for the “hello world!”.
Buttons840
Saw this mentioned in a HN comment and thought it deserved more attention: https://news.ycombinator.com/item?id=34106174
atiedebee
Skimming through the pages, there is some things that aren't really accurate.
> Integers - whole numbers which can be either positive or negative. Defined using char, int, short, long or long long
char is either signed or unsigned depending on the platform/implementation. Use signed char if you want signed integers.
Telling people who are new to C to define booleans with macros is not a good idea, as they have had a proper implementation since c99.
It also feels weird to treat structs and pointers as advanced topics. They are basically required to be productive in the language.
stdint.h was introduced in c99, not c11.
Explaining bitwise operators as "bitmasks" is also quite weird. Bitmasking is just one of the few things you can do with them.
> In C, functions must be first defined before they are used in the code. They can be either declared first and then implemented later on using a header file or in the beginning of the C file, or they can be implemented in the order they are used (less preferable).
This paragraph reads weird. I haven't found any place where the tutorial mentions how to properly write header files. It might be because of the interactive part, but if that is the case then this tutorial doesn't really teach you how to program in C because the tooling around it is an important part of actually using the language. It is also fairly common to declare functions in order of use. Discouraging that is like telling people they need to use tabs over spaces instead of actually focussing on language semantics.
fuhsnn
> Defined using char, int, short, long or long long
> Note that C does not have a boolean type
`_Bool` and `long long` are both introduced in C99, this is mixed up info.
Edit: probably tailor-made for old MSVC, which didn't support _Bool until VS2013.
PaulRobinson
Ironic that you've drawn the eye to the thing that needs to be front and center of any C tutorial, and also the thing that makes C so tricky to work with.
When somebody says "This program is written in C", my initial thought is "Which C?". There is no one, single C.
I don't write C daily. Heck, I don't write it monthly any more. And so my grey cells are struggling with which versions introduced what, and you've spotted something I would have missed on a first read.
And this is a problem.
Can you list all the undefined behaviours, and which language features came into which version across ANSI, C99, C11, C17 and C23? The last one feels a little brighter in my mind, but I definitely can't, and if I was writing a C tutorial - like many that have been written - I'd probably be explicit about choosing a version and sticking with it, and good luck and godspeed to everything outside that version.
Of course this is one of the reasons learning C is harder than other languages, and why languages like Zig and Odin have a decent chance: ergonomically simpler than Rust, all the power and flexibility, (much) less of the head scratching.
card_zero
Because Zig et al won't have future versions with new features?
PaulRobinson
Sure, but C predates semantic versioning and is rammed with undefined behaviour that a lot of people depend on.
Modern languages - even those that have high levels of C interop like Zig - can (and do) avoid those problems.
jononor
Of course. But they are starting with 40 years less baggage. And can reasonably assume a modern hardware architecture, for example.
arp242
I think you will always have this sort of thing for anything that's primarily driven by a standard (e.g. C, but also most web stuff) versus anything that's primarily driven by one specific implementation (most other languages).
Things are a lot better today than they used to be though: compilers that don't support modern features are rarer, and the compilers give much better errors on things like UD.
anovikov
Unbearable with ads all around.
zerr
Surprising that there are still people without ad-blockers. Just install uBlock Origin.
commandersaki
The interactive editor seems to only use a quarter of the screen space and isn't resizable. Quite vexing to use.
eigenvalue
When I see a page filled with junky ads like that, I instantly close it. On mobile especially, it’s unusable.
I’m amazed something like this gets traction here.
shric
I get no ads as I've been using ad blockers for as long as I can remember.
It is, however, a terrible tutorial (it's full of beginner errors made by people who don't understand C but think they do based on behavior by whatever compiler they're using at the time).
There is presumably some correlation between sites riddled with ads and having terrible content. Perhaps ad-blockers should show how many ads they have blocked more prominently.
user432678
Most of the users of this website probably run ad blockers, thus the traction. Bu I agree.
xnickb
I didn't see any ads. Thanks for letting me know
null
codr7
The more, the merrier, here is another one I've been working on lately:
null
doublerabbit
The issue I always find with these tutorials that they never seem explain the finer details.
On the Array Page:
/* print the 7th number from the array, which has an index of 6 */
printf("The 7th number in the array is %d", numbers[6]);
There is no mention of what %d is or does. Once you know, it's fine, it's the display placeholder for the variable but that's what throws me off on tutorials.
alabhyajindal
I need to brush up on C for my dissertation. How does this compare to Head First C?
I read the first chapter of that book and loved it! Very unlike other books on C which dedicate an entire chapter to `for` loop for instance. How do other programmers even read a book like that? Isn't it tiring to read through how a `for` loop works for the 70th time.
mdaniel
> I need to brush up on C for my dissertation
My condolences on the first part, but congratulations on your dissertation!
Borzadaran
Interactive tutorials are great for lowering the entry barrier, but technical accuracy is crucial for beginners. It's suggested to stick to a single C standard (like C99), properly cover essential topics like structs and pointers, and prefer _Bool over macros for booleans. Overall, the effort is appreciated.
As great as this looks, I think it should heavily emphasize moving on to using GCC (or maybe LLVM).
I learned C in the mid nineties using a copy of Visual C++ 1.0 that a friend had gotten from his father (and probably he got it from work). It was the only compiler I knew of and once I was ready to move beyond toy programs, I was seriously hampered by the fact that this compiler couldn't produce text mode executables (any call to printf opened its own new window that definitely wasn't cmd.exe) and it couldn't set the graphics mode for blitting pixels. It was heavily oriented around this new fangled MFC thing but I was a teenager so I wanted to program games not business apps or whatever. That meant I wanted text mode or graphics mode.
My high school CS class had Borland C++ and I could set mode 0x13 with that in DOS. But I had no way of obtaining this compiler as a kid. And it probably didn't work on Windows 95 anyway.
Anyways, it wasn't until the early 2000s that I finally learned about GCC, a free as in beer and freedom compiler and the simplicity of it would have been amazing for learning.. If only I had known.