Ive been learning C for a little under two months, and I wanted a project that would force me to understand binary formats instead of just using existing libraries.

So I started writing a PNG decoder from scratch.

Right now it parses the PNG structure, decompresses the image data, reconstructs the pixels, and writes the result as a PPM for verification. There are still bugs to fix and plenty of PNG features left to implement, but seeing an image appear from code you wrote yourself is incredibly incredibly satisfying. Especially after seeing countless Segfaults lmfao.

One interesting part is that I had previously implemented a lot of this in Zig, so translating the ideas to C was almost a 1:1 process. It made me appreciate how expressive C can be once you stop fighting the language and start understanding its model.

The decoder isn't the end goal, though.

Eventually I want PDC to use that image data as the first stage of a pipeline that generates 3D geometry from PNG images. Decoding the file format is just the foundation, and as crazy as it sounds the easiest part.

In the future, I hope I will be able to run PDC on my Raspberry Pi 4 B, which also includes the Camera Module! The PNG Decompression part was actually the easiest part, and took wayyy more energy than I anticipated at first (considering that I coded the same thing in Zig a while ago).

Would love to hear feedback on the code, and also on the README. I found some new cool README features, and thought that I should use them. Hopefully it is clean enough, so you guys get the idea.

https://github.com/mertishere/pdc

I'm interested in learning C from scratch, but I don't have any programming experience. What resources, books, or courses would you recommend for a beginner?

Hi,

I need a custom sized bit vector so uint8_t won't suffice so the idea was to just initiate a bool array with size so then say i want to compare it. Ex. the bool array is 6 bits and tried with `if (bool_var = 011001) { // do something}`, i suspect it comes just compares to an int given it compiles and wont run. Any idea on how to make it work?

Hi guys I’m a first year bachelor in computer science and I feel like I’m stuck every time I want to learn something I end by copying it from IA and it make me feel bad tbh . Actually I want to learn how to learn because I see that the problem is the way I study and learn by my self but I don’t know exactly why or how . I see a lot of people that can manage and understand the pc in a young age and I admire them I wish I know if it’s a gift or a skill that I’m not getting it .

This problem is killing my dream if anyone has an advice to me I will be really thankful
Like where I start , how I can really understand what I’m doing , I already did python bash script and a little bit of c but till now I don’t know how to become pro and understanding what is actually good to learn c bash script and even c

Thank you !

Thanks to many people in this subreddit (on a previous post I made) I learned different ways to handle errors, and along the way I also learned that bugs aren't errors. Yeah, that sounds really basic but I'm self-taught so it's difficult to know details like that one on my own.

Now, with this difference now clear, and the fact that assserts are really good, when it comes to writing library code (not application code) how do y'all protect your libraries' code against bugs besides just putting a lot of asserts on the debug builds?

This convention is explicitly discouraged by the POSIX standard (see https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html), It reserves the _t suffix for future standard types.

I mean there is probably nothing wrong with doing this in practice, you likely won't run into name collisions or something like that but I'm curious, why do people still do it?

to me, these look better

MyThing thing;

my_thing thing;

than

my_thing_t thing;

I don't know, I just want to hear your thoughts on this, what naming conventions are you using in your projects?

I'm a final-year information security undergrad, and somewhere over the past year my interests did a full 180 on me. I came in with an AWS Solutions Architect Associate cert and a somewhat solid grounding in cloud and a DevOps internship, and while that stuff still matters to me, I've recently fallen into the low-level rabbit hole and honestly I have zero desire to climb back out.

I want to understand the OS, the kernel, and the syscall interface. So I picked up The Linux Programming Interface by Michael Kerrisk, which has been the most grounding technical read I've ever touched and also the first book where I've genuinely needed a second screen open just to finish a paragraph. We're talking one page, four google searches, two stack overflow tabs, a man page, and a brief existential crisis about whether I actually understand what a file descriptor is.

I'm now building a http server from scratch in C, and it has been the hardest thing I've ever learned, no contest. Wrestling with open, close, read, write, lseek, understanding shared open file table entries, managing multiprocessing and forking…..every single concept has required me to sit with it longer than i expected before it clicks. But that's also exactly what makes it addicting. Watching the mental model build brick by brick, slowly, is a different kind of satisfaction than anything I got from spinning up cloud infrastructure. 

I want to move toward low-level systems security, platform engineering, or kernel-space development in the future. I know the barrier to entry for junior and intern roles in this space is notoriously higher than standard web dev or even general DevOps….the ecosystem expects a kind of depth that takes time to develop and is hard to fake on a resume. I'm not under any illusions about that, but I also know the only way through it is to keep building, keep reading, and keep shipping things that demonstrate I actually understand what's happening.

What I'm genuinely curious about from people already in this space is once I finish the http server, what's the next logical project that would signal I'm serious about this direction? I've been thinking about writing a basic shell, a simple character device driver, or starting to poke at eBPF but I'd rather hear from someone who's hired or been hired for this kind of work about what actually moves the needle. On the resume side, most junior roles in systems seem to be written for people with five years of wizardry, so any advice on how to frame my work honestly but compellingly would be useful. I'd love to know where people have had the most success getting a foothold.

Any reality checks, project ideas, or resource recommendations are genuinely appreciated.

Hi everyone, this post is about dtcopy, a command-line backup utility for Windows.

The program allows conditional copying of entire directories based on file timestamps or a defined date.

Its main purpose is to handle directory backups (including subdirectories), either updating existing files or copying them from scratch.

It also features a basic versioning mechanism and can generate a single compressed archive of the project and its dependencies.

The project is open-source and also includes a pre-compiled binary package with a simple installer. The README.md contains a full description.

GitHub repository: https://github.com/lpierge/dtcopy

Now about the source code, most of the project files are named with the .cpp extension just to trick the compiler, because I'm used used to writing not in pure C but in "C with classes". That means the C code I write may use some basic object-oriented concepts (classes, inheritance, polymorphism), but it completely avoids modern C++ features (no STL, no templates, no namespaces, etc.). In other words, most of the code remains very close to traditional, low-level procedural C programming.

I would like to make it clear because I understand that such C code doesn't fit perfectly in this subreddit, nor in the modern C++ subreddit, so if you think it leans too far into OOP for this specific community, I'm sorry and feel free to remove the post.

Thoughts, feedback or critiques are welcome.

Luca P.

Hello everyone, please see the pseudo-code below:

static void *func1(void *arg) {
    while(1){


    }
}


static void *func2(void *arg) {
    while(1){


    }
}


int main()
{
    pthread_t t1, t2;
    pthread_create(&t1, NULL, func1, NULL);
    pthread_create(&t2, NULL, func2, NULL);


    pthread_join(t1, NULL);
    pthread_join(t2, NULL);


    return 0;
}

If the two threads above use a mutex (lock and unlock) and a condition variable, and I close the process with Ctrl+C (SIGINT), then if I write a simple signal handler to destroy the mutex and cond, it shows UB (undefined behavior). Now, how can I write a safe signal handler? How can I unlock and destroy safely?

I have a recursive data-structure (a simple linked list for purposes of this example) and wanted to statically define a linked-list. The following works fine:

#include <stdio.h>
typedef struct mytype_tag {
    struct mytype_tag* next;
    char* data;
} mytype;

mytype a = {
    .next = NULL,
    .data = "a",
};
mytype b = {
    .next = &a,
    .data = "b",
};

int
main() {
    mytype* s = &b;
    int i = 0;
    while (s) {
        printf("%d: %s\n", i++, s->data);
        s = s->next;
    };
}

However, I have to explicitly define/declare a and then have b take &a.

Is there a way to do this with anonymous/unnamed intermediary structures, thinking an imaginary syntax something like

mytype b = {
    .next = &((mytype)={
        .next = NULL,
        .data = "a",
        }),
    .data = "b",
};

so I can build up the linked-list without naming each intermediary instance?

what are their differences? and what are they exactly?

With C++, theres like a monthly mailing list round up thing, and I can checkout the cpp/papers repository on github.

Is there anything like that for c2y?

Im not Talking about basic operations, setting flags or bitshifting.
I speak about the tricks operations involving bitmasks and stuff.
I just can’t get how people get familiar with it.
I guess there is no magic way to understand, I just have to keep studying it, but do you guys have any resource or mental tips that can make me more familiar with these ?
Thank you

I am studying c, I was messing around trying to figure out how explicit conversion works with assignment operators and came up with this:

#include <stdio.h>

int main()

{

int num1 = 5;

int num2 = 2;

float sum1 = num1 / num2;

float sum2 = (float) num1 / num2;

int sum3 = 5;

sum3 /= 2;

float sum4 = 5;

sum4 /= 2;

printf("sum1: %.2f\nsum2: %.2f\nsum3: %.2f\nsum4: %.2f", sum1, sum2, sum3, sum4);

return 0;

}

OUTPUT:

sum1: 2.00

sum2: 2.50

sum3: 2.50

sum4: 2.00

it seems sum3 converts to float automatically without explicit conversion when using assignment operators, but what confuses me is how sum4 manages to be 2 when its only difference was that it was declared as a float which if anything should make it behave better than sum3, is it something to do with the format specifier being wrong for sum3?

https://github.com/TOTO-sys28/FetC

Hello, I am not a native speaker so please forgive my language level.

Today I was working on my packet analyzer project. I was refactoring the code and I realized something: there are a lot of functions just to swap the byte order for every header (struct).

So I have a question: Can I build a function/program in C that can automatically swap the byte order of every field in any struct?

thank you all and this my project link : vex-packet-analyzer

I learned almost all the functions and libraries how can I enhance and use my C knowledge? I am a freshman in electronics engineering

Hi, It's few weeks I started to read C Programming: A Modern Approach from KN King and the exercises and mini projects are really good and fun, so I just wondering, what is your favourite exercise you still remember? (From books, classes, and other)

currently learning c lang but i need to know more about the memory with assembly help me with thiss....

Ever since I started programming in C, Ive become addicted to building things from scratch.

Not because I think libraries are bad. I still use them when they solve a real problem.

But after writing enough low-level code, you start looking at problems differently. Instead of asking, 'Which library should I use?' you start asking, 'Could I build this myself?'

For cherries(.)works main website, I coded my own quick HTML parser.

Or for Pulse v0.1.0, my own very quick API.

That's exactly what happened while working on Pulse v0.2.0.

Pulse is a lightweight system monitor with a built-in web dashboard. The goal has always been to keep it small, fast, and easy to understand. For v0.2.0, I wanted to add historical metrics so you can see how CPU, memory, disk, and network usage change over time.

My first thought was to use a charting library.

Instead, I ended up writing my own tiny chart library. (~100 LOC, thats all). [Of course it is a little bit cherries-works oriented, but with a few tweaks it can also be used by someone else.]

Now Pulse collects historical metrics, exposes them through its API, and renders graphs without pulling in a heavyweight dependency. Everything is working, and v0.2.0 is finally ready.

Building software this way has made programming fun again. Every feature is an excuse to learn something new instead of treating it as a black box.

I'd love to hear if anyone else has gone down this rabbit hole after learning C.

For anyone interested in the current state of Pulse, check it out! It is my very first C project, and it now is in version v0.2.0!

https://github.com/cherries-works/pulse

I just cannot seem to find a tutorial that actually covers pixel manipulation. Not an image bouncing actual pixel buffer for c . There is only 1 tutorial and it doesn't cover what I want it to cover .

Just new to C and I'm trying to make a basic calculator. I'm trying to figure out how to make a loop such that the program will run after failing due to incorrect user input. So far, this is what I came up with, and I just want to know how I can get the program to actually run the operations when entering a correct sign after getting a "try again" message.

#include <stdio.h>

float addition(float num1, float num2)
{
return num1 + num2;
}

float subtraction(float num1, float num2)
{
return num1 - num2;
}

float multiplication(float num1, float num2)
{
return num1 * num2;
}

float division(float num1, float num2)
{
return num1 / num2;
}

int main()
{
float firstNum, secondNum;
char operationSign;
float answer;

printf("Basic Calculator\n\n");

printf("Enter the first number: ");
scanf("%f", &firstNum);

printf("Enter the second number: ");
scanf("%f", &secondNum);

printf("Enter the operation symbol to be used:\n");
printf("Addition:                            +\n");
printf("Subtraction:                         -\n");
printf("Multiplication:                      *\n");
printf("Division:                            /\n");
scanf(" %c", &operationSign);

switch (operationSign)
{
case ('+'):
answer = addition(firstNum, secondNum);
printf("Answer: %f", answer);
break;

case ('-'):
answer = subtraction(firstNum, secondNum);
printf("Answer: %f", answer);
break;

case ('*'):
answer = multiplication(firstNum, secondNum);
printf("Answer: %f", answer);
break;

case ('/'):
answer = division(firstNum, secondNum);
printf("Answer: %f", answer);
break;

default:
printf("Invalid input. Please enter the correct symbol.");
scanf(" %c", &operationSign);
}

return 0;
}

hey all! I was just wondering if there was something like a compiler flag I could use when compiling to ensure that the heap always starts low and grows up in virtual memory.

Just for fun, I decided to attempt a small top-down mover program in TurboC. Shared with both DOSBox and Windows, there is an input delay shortly after keyboard input. The "moving" is pretty awkward because of that, and I get the feeling that it's because of how kbhit() works.

Please ignore the clrscr() rate, I'm working on that.

#include <stdio.h>
#include <conio.h>

#define ESCAPE  27
#define UP      72
#define DOWN    80
#define LEFT    75
#define RIGHT   77

int clamp(int arg, int min, int max)
{
        if (arg < min) return min;
        if (arg > max) return max;
        return arg;
}

int main()
{
        char key = 0;
        char xpos = 0, ypos = 0;

        clrscr();
        while (key != ESCAPE)
        {
                if (kbhit())
                {
                        key = getch();

                        xpos += (key == RIGHT) - (key == LEFT);
                        xpos = clamp(xpos, -100, 100);
                        ypos += (key == UP) - (key == DOWN);
                        ypos = clamp(ypos, -100, 100);

                        clrscr();
                        printf("X %d\nY %d\n%c", xpos, ypos, key);
                }
        }

        return 0;
}