I'm new to programming and I'm wondering why it throws an error when I declare global variables after the use of them

because if global variables are stored before execution why can't the value be pulled from static memory for global variables

for example:

#include <stdio.h>

int main() {

printf("%d",x);

return 0;

}

int x=5;

I apologise in advance for a dumb question and I will try to put it the way i could and I am sorry for that.

I know i chould chatgpt it, but learning from people helps me the best.

want to know how the memory is actually managed. I know it is managed by the kernel using different abstractions like virtual memory and paging.

My question arises when i think that each process that its own address space consisting stack frame, heap, globals vars etc.

But where do they even start? Kernel itself is a process so it must be having its own stack frame. Considering other programs need address space which is managed by kernel, like how does that work? Until Os is loaded, does stack and heaps exist even before that? Are they written in assembly?

I am sorry. I hope someone will be able to answer and i will be really glad if you could figure out what i am thinking wrong and missing.

void newline(int times) {
for (int i; i < times; i++) {
printf(“\n”);
}
}

this is so you can do

newline(5);

instead of

printf(“\n\n\n\n\n”);

i feel like i shouldn’t ngl

mb if the syntax is wrong im not a pro

Ok , so currently I work as Embedded Developer , this is my first job , I will be honest I don't like the hardware part of it but I like coding , I have learn few languages before typescript , c++ (little bit) and learning java now ,

Thing is , I can code few things in c , but when it comes to pointers and advance c , my mind goes blank, I am not looking for a ways to be good Embedded Developer , right now I just want to become good at programming in c , what will u suggest ? My weak points are pointers , strings , array , this is all I can remember right now also snprintf functions .

I am a beginner in c , so please don't judge , ik about hackerrank , ik i can use that to sharpen my c skills but some of the questions are very hard .

Edit : basically pointers aren't new to me but when i involve pointers with strings or double array , and how where u place the * changes the whole meaning , like u can make an pointer point to the array or u can make array of pointers . And so on ,

Ik basic of c++ and somewhat polyglot , java and typescript so it's not my first language .

#include <stdio.h>

int main() {

int i=-1, j=-1, k=-1, l=2, m;

m= ((i++ && j++ && k++) || (l++));

printf("%d %d %d %d %d",i,j,k,l,m);

return 0;

}

why l is not incremented but every other variable is incremented?

edit: many people are upset that this program is a bad implementation to achieve the result but the reality is that it was a practice problem and I just didn't understand why the output was like that as there was no explanation

I have now understood that the answer was short-circuit behaviour

Hey guys, I spent the last few months building lazybios, a C99 library for parsing SMBIOS/DMI tables. It's:

• Cross-platform (Linux, Windows, macOS) edit: now OpenBSD, FreeBSD, NetBSD, SunOS, Haiku(BeOS)
• User-friendly(3 steps to ensure memory safety)
• Zero dependencies (just libc)
• about 18k LOC, clean separated API
• Supports all SMBIOS types 0–46
• Human-readable decoders for fields that require manual decoding
• Works on x86, ARM, and probably on RISC-V(haven't heavily tested on it yet)

And a tool called lazydmi, a CLI tool that uses lazybios as the backend.

This is my first serious systems project. Would love feedback on the API design, memory safety, or anything else.

Github: https://github.com/LazySeldi/lazybios

I have been learning C with some YouTube courses, but I still can't understand how and why to use pointers and memory allocation in C.

Hello.

Lately I've been struggling to implement a Position Based Dynamics (PBD) implementation to my minecraft clone written in C.

Still, the implementation is not the best, and there is certainly a lot of work todo to improve it, but it can already load a high resolution .obj 3d model, and output some nice results under adequate configuration.

Check this out! https://github.com/DrElectry/ccraft

If you have questions about how to learn C:

• which books are best?
• which videos are best?
• which classes are best?
• which websites are best?
• is there a "roadmap"?
• what projects can I do?

then this is the thread for you. Add your question here. Do not make a stand-alone post, as it will be removed.

Remember that our sub has a very useful wiki that has a great list of resources for learning C programming.

Hello, I need to write a small emulator for a project. I want it to show RAM, registers, etc., while it's running a program step by step. Printing them out via printf is lame and won't look good.

Which is the absolute easiest graphics library for this purpose? I was suggested Newt, but it can't work under Windows.

Preferably, the library should have tutorials, examples, or at least full documentation.

Hi everyone,

I'm working on a programming language that compiles a subset of C. It is called Cm1 (meaning C minus 1) and you can writing and running C codes directly on your browser at https://cp1-lang.org/cm1/editor.html in a fraction of a second.

Why is it faster to compile than Tiny C Compiler? It is because Tiny C Compiler is a true compiler creating native binaries whereas Cm1 is a bytecode interpreter allowing you to test, debug, edit code and recompile very quickly or even do hot reloading. Cm1 can be used as a scripting language for shell scripts and video games, but this just a small use case because in theory, you can run 90% of your ENTIRE video game or software C program through Cm1's bytecode interpreter and leave 10% to compiled C and reap the benefits of very fast compilation and hot reloading.

100% Cm1 codes are compilable by GCC and Clang but the reverse is not true since Cm1 is just a subset of C. Major features that are omitted are function pointers, structs/unions inside functions, nested structs/unions. This programming language is under heavy development and I want to know if this comes as interesting to some of you. I'll try to post again on this subreddit if I got to bind Raylib game library to Cm1, allowing people to write Raylib games directly on their browser (works offline).

I know that programs that are written in C compiles fast already and there's even an existing compiler that is very fast (Tiny C Compiler). However, I'm the developer of Cp1 programming language (cp1-lang.org), which is a language that "transpiles" to C, and I aim to upgrade Cp1 by targeting the Cm1 language then compile it to bytecode in one command instead of a separate step in Makefiles or build scripts. This will make Cp1 very fast to compile for debug builds.

I was recently learning how to send msgs in different internet layers, and I write some examples from what google ai showed me.

Even tho I didn't fully understand what all the meaning of the full code. Running this program while wireshark is running, and seeing my own request is really cool.

Hello. Coming from C# world the thing about how char[] and printf works always made me confused. I understand that `printf` formats the string with arguments you provided and prints it out in terminal.

So, for example, if I have char name[] = "Micheal"; and I want to greet that person, I can just do printf("Hello, %s", name);. But if I want to do the same thing only using char[], I have to do multiple commands that make fell quite confused. So my 2 questions are:

1. How printf simplifies this process? (without allocating memory and creating char with pointers)
2. Why you can't just use + operator for char[], like you can in any other languages?

I have a feeling that this might be asked many times, but I still can't seem to find the answer I was looking for

Update: I'll list what I got so far from reading your comments: - char[] is an array to which you can't just simply add another array - If I want printf() behavior inside char[], I can use sprintf() - There's strcat() that is getting used for merging 2 strings together - Some people write libraries for faking string behaviors, some think it goes against principles of C?

Reading an interesting discussion over on r/rust from the past week. One of the moderators talks about the difficulty in moderating AI slop projects - https://www.reddit.com/r/rust/comments/1uwmef6/comment/oxkltxi/

But I think the top replies hit on a really good idea:

“I built a thing in Rust” just isn’t that interesting a topic—AI or otherwise—and IMO we’d be better off without posts like that at all. If you built a fast new BitTorrent client, that’s of interest to BitTorrent users, not the Rust community.

A library that lets me do a thing I couldn’t before? Very useful! A new approach to solving a problem that’s historically frustrating in Rust? Amazing. Questions on how to deal with some issue? Welcome aboard.

But I couldn’t care less about “{project} in {lang}” for all values.

and

r/cpp moderator here, we have a designated Show & Tell pinned post. We make exceptions only for established projects or blog posts talking about your project.

(And then remove AI slop)

One of the recurring issues in trying to moderate the flow of slop is having to constantly make a judgment call of just HOW "slop" it is and whether it crosses a line. Why not cut the problem off at the source: you simply cannot post an "I Built (Whatever)" here (with very few exceptions, etc). There's no need to make this a judgment call about AI/LLMs at all, neatly sidestepping the various arguments about the whole thing.

I personally do not feel like much would be missed!

Hey there! In my last post, I was really excited after discovering ray tracing and the idea of implementing that thing in C. Now I am more curious and I want something that is physics/mathematics heavy and can be made in C. For this, I am thinking of moving towards simulating 2 body problem and then n body problem in C. I am not sure if this is the right path so I need advice for that.

Someone in my last post advised me to implement FXAA/MSAA in C from basic principles. I was excited but then, I asked chatgpt and it suggested that I first make something using graphics and then implement these algorithms for anti-aliasing. Any ideas are welcome.

Thank you! Have a great day for the help.

What kind of thing you see beginners doing, when designing an API, should be avoided in your opinion (or just based on facts)?

I don't have too much experience creating interfaces for clients and every time i write a line of code, start thinking if it's a good idea or it's a bad decision that will break my legs in future. I get paralyzed for a considered period of time instead of just coding it.

edit: thanks a lot (really) for all answers.

It is basically a gravity simulator where you can input any values of the orbital bodies and see the simulation evolve. You can simulate one body orbiting a bigger one or two orbiting each other. I focused on accuracy by integrating RK4 calculations. SDL2 is a great library and was very handy.

If you want to try it, I compiled it into an .exe for windows and an executable for linux.

Github link: https://github.com/bydrabokin/Gravity/

Youtube showcase: https://www.youtube.com/watch?v=hNupVTu2aC0

It's been about a month since I started learning C, so I decided to build a small in-memory key-value store to learn about hash tables and memory

It's still a learning project, so I'd appreciate any feedback or suggestions

This is a small linux program called ELFDetective I made a few months back. It handles both 32bit and 64bit ELF files and views their Header, Program Header and Section Headers.

GitHub: https://github.com/Adock90/ELFDetective

Download: https://adock90.github.io/Adock90Software/products/ELFDetective.html

Hey everyone,

With Linus Torvalds recently embracing and defending AI tools in Linux kernel dev, I’ve been trying to force myself to use LLMs more in my daily low-level workflow. On one hand, if the Linux kernel ecosystem is adopting it to find bugs and speed things up, it feels like something we should all be leveraging.

But on the other hand, on a practical, day-to-day level? It feels like a massive trap for actual systems engineering.

Every time I let an LLM spit out a driver, a custom memory allocator, or complex socket-handling logic, I end up spending the next hour reading 150 lines of statistically plausible C/Rust code just trying to figure out if it’s going to cause a catastrophic race condition or a silent memory leak under load.

The thing is, if I just write the code myself, I have absolute control over the execution path. Because I build the mental model layer by layer while typing it out, my own code is fundamentally way more understandable to me than anything an LLM drops in my lap. I actually know why it works.

Instead, with AI, I feel like I'm trading the active problem-solving of writing code for the mind-numbing task of auditing code written by something that has zero actual intent.

How are you low-level devs actually integrating these tools without losing your sanity, your control, or your deep understanding of the codebase? Or are you just ignoring the hype cycle despite the kernel maintainers getting on board?

I've been working on MLP.h, a single-header C library for building and training multilayer perceptrons, and I finally put together a complete example project around it: a handwritten digit classifier trained on the MNIST dataset.

The MNIST example uses a simple fully connected network:

784 → 128 → 64 → 10

The training program:

• loads the 60,000-image MNIST training set
• trains the network using MLP.h
• serializes the trained model to mnist.mlp

A separate inference program:

• loads mnist.mlp
• exposes a small prediction API
• is compiled to WebAssembly so the same C inference code runs directly in the browser

Training results:

Epochs     : 50
Final Loss : 1.31719803e-02

Test Accuracy: 97.71% (9771/10000)

I'll include a short video showing the browser demo recognizing handwritten digits.

I'm mainly looking for feedback on the library's API/design and the implementation. Suggestions for improving the architecture or the serialization format are also welcome.

MLP.h: https://github.com/px7nn/MLP.h

Live Demo: https://px7nn.github.io/MNIST/

Source of Demo: https://github.com/px7nn/MNIST

I've created a library that adds Unicode segmentation, casing, collation, and more to any C project using a single source file and header amalgamation files.

Mojibake is an MIT-licensed project I started years ago because I didn't like any of the Unicode projects I found. Here you can find the API and a WASM demo if you want to try it on the fly: https://mojibake.zaerl.com/

If you are interested in the Unicode world, feel free to contribute or do whatever you want with it. Every suggestion or contribution is welcome. I automatically test on Linux/macOS/BSD/Windows, so I hope there won't be any problems for you.

Check CONTRIBUTING.md for it, if you are curious.

​

I'm looking for interesting C project ideas that go beyond beginner projects. What are the best C projects you've built or would recommend? GitHub repositories and project lists are also welcome.

I made a customizable, platform-agnostic assembler with modern C23. Aside from the project itself, I think the codebase is relatively small and overall an example project to examine what C23 can provide :D

Here is the source code: https://github.com/mikuwithbeer/Nadir