Where is tutorial to C?

C - OOP-language for structure, where we don't know all objects and actions (e.g. microservice with 10+ integrations or Arduino).

A = (int **)malloc(n * sizeof(int *));
    for (int i = 0; i < n; i++)
        A[i] = (int *)malloc(n * sizeof(int));

    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            if (sqrt(Vert[i] + Vert[j]) - (int)sqrt(Vert[i] + Vert[j]) < 0.001) A[i][j] = 1;
            else A[i][j] = 0;
        }
    }

1. Let's start to decrypte some example: * - array, **-decart array. We don't use some useful words for creating cycle
2. Variables i/j making cycle more ordered without much descriprions
3. Conditions if/else don't put our variables values, but initialize temporary memory 0/1 (like false/true eng)

    ofstream answerFile;
    answerFile.open(file_name);

    for (int i = 0; i < n; i++) {
        answerFile << Vert[Path[i]] << " ";
    }

    answerFile.close();

Files - memory with undetectable type of variables (e.g. .doc/.txt/.img).
I'm using several algorithms for opening/closing files with library fstream.

class Graph
{
private:
    std::vector <int> Vert; 
    int **A, n; 
    std::vector <int> Path; 
    std::vector <bool> Visited; 

Don't forget creating 2 different types: .h - header file; .c/.cpp - working file. It's help compiler handle exceptions more quickly.

Class Graph defines memory area under some variables and functions. Decart array "A" and integer type "n" are identified like part of class. Fuctions Vert and Path will work inviseble to the user (Cos private path). And Visited will have values 0/1.