#include <iostream>

int main() {
    int arr[3][4];

    //  having the { on the same line as for example "for" and "if" is a more generally accepted style.
    for (int i = 0; i < 3; i++) { // it's nicer to have a space after the "for", and also "if" et cetera, because it's more readable.
        for (int j = 0; j < 4; j++) {
            arr[i][j] = i * j;
        }
    }


    // I made the code look a bit weird below to make it easier to comment.

    for (

        int (*p)[4] = arr;  // creates a pointer to "arr". This is basically p[0]... (I guess p[0][4] is a better explanation.)
        p != arr + 3;       // checks if the current index of the array "p" is less than 3 - so it doesn't go out of bounds
        ++p                 // increment the pointer by one so that it goes one up. Before you call ++p, it is at p[0], but when you call ++p - it will become p[1]. It increments the index of the array.

        ) {

        for (

            int *q = *p;    // pointer to array that the current index of p is at. so if p is at arr[1], then q becomes arr[1][0].
            q != *p + 4;    // checks if the current index of the array "q" is less than 4 - so it doesn't go out of bounds
            ++q             // increment the pointer by one so that it goes one up. Before you call ++q, it is at q[?][0], but when you call ++q - it will become p[?][1]. The ? is basically any index that p is. an "i" if you will.

            ) {

            std::cout << *q << ", ";    // prints out the value of the current index of q. q got first assigned to as the index of p, but remember we incremented the q pointer? This is arr[p][q] - so it's the element.
                                        // the * before q deferences the pointer and you get the value that the pointer points to.
        }
    }

    std::cin.get(); // system("pause") is not recommended

    return (0); // it's nicer to have pharanteses around the return value.
}