Passing pointers (matrix) to a function in c [dupl

This question already has an answer here:

Passing an array as an argument to a function in C 9 answers

I have dynamically created a matrix using calloc in the usual way:

int **matrix;
int dim,r;
scanf("%d",&dim);
matrix=(int **)calloc(dim, sizeof(int *));
for(r=0; r<dim; r++)
   {
    matrix[r]=(int *)calloc(dim, sizeof(int));
   }

Now if I wanted to create a function to just print the elements of this matrix, I should write something like:

void stampmatrix(int **matrix, int dim)
{
int r=0, c=0;
for(r=0; r<dim; r++)
    {
    printf("(");
    for(c=0;c<dim;c++)
        {
        printf(" %d , ",matrix[r][c]);
        }
    printf(")");
     }
}

And this works fine. Now I add this line to the previous function

`...`
 matrix[r][c]=1;
 printf(" %d , ",matrix[r][c]);
 ...

If i call this function in my main function, stampmatrix(matrix,dim) once i run the program, the compiler should create a copy of my matrix, fill it with 1, and then print them, and then return to my main function without changing the actual matrix. But if I do this and then i check in my main function the values of my matrix elements, they are changed to 1. In class i was told that if I pass values to a function, the program creates a copy of the values, works with them and then cancel the copy, so I need to pass addresses to a function in order to actually change the contents of my variables in my main function. Why in this case it doesn't work, and changes my matrix values? It's because I still pass pointers to the function stampmatrix? I really don't understand. Shouldn't the function be something like:

void stampfunction(int dim, int ***matrix)

Or it's because i used a void function? Thanks for the attention!

Remember, in this program (I assume), all code shares the same heap (memory), and pointers are kind of like signposts, to that heap.

What the method

void stampmatrix(int **matrix, int dim)

does is like when you give a person a number, dim, and physical map to, say, all the signposts to apples in a grid.

So yes, you passed in by value directions to the matrix - you gave a person a copy of your apple-signpost-map.

The other thing you did is that matrix[r][c] implicitly dereferences the pointer - or, the method is saying to follow the apple-signpost-map directions all the way to point (r, c) in this grid.

So when you say `matrix[r][c] = 1', you're saying to make sure there's only one apple at (r, c) when you leave. That's why the value at matrix[r][c] changed.