Two dimensional arrays and pointers

Question

I have the following code snippet:

char board[3][3] = {
                     {'1','2','3'},
                     {'4','5','6'},
                     {'7','8','9'}
                   };

printf("address of board : %p\n", &board);
printf("address of board[0] : %p\n", &board[0]);

Both printf() statements all print the same value: 0x0013ff67

1. As per my knowledge, board (i.e) array name represents the address of the first subarray (i.e) board[0] and

2. board[0] represents the address of first element in the first array (i.e) board[0][0]

Why am I getting the same address in all my printf() statements? I expect different addresses for both statements.

I am pretty new to this stuff and don't understand this behavior. Kindly enlighten me.

Answer 1

Though it's a 2D array, inside the memory it will be represented as linear array. so when you say, board[0][0] it still points to the first element in that linear array and hence the same memory address.

Answer 2

As per my knowledge, board (i.e) array name represents the address of the first subarray (i.e) board[0]

This is only true if board is used outside of these contexts

• As operand of the & operator
• As operand of sizeof

When any of that applies, expression board represents the array and keeps having the type of the array (char[3][3]). Applying the & operator to it results in getting the address of the array, which of course equals the address of its first element, merely having a different type (char(*)[3][3] instead of char(*)[3]). The same that is true about the array board is true about its first sub array board[0].

When you use it outside of those contexts, you get the address of the first element (subarray in your case). That address is not an object but just a value. Value have no address, but objects have. Trying to apply & on it would fail. For example

// error: trying to apply '&' on something that has no address
&(1 ? board : board)

Note that anything said above applies to C; not necessarily to C++.