Pointer and 2D array

2.  In a two dimensional array, we can access each
element by using two subscripts.
first subscript represents the row number and
second subscript represents the column number
second subscript represents the column number
 Consider the following declaration statement,

3.  The above declaration statement creates a 3x4
matrix initialized with the following values:

4.  The element at ith row, jth column can be
accessed using
a[i][j].
 To access the value 7, we have to use
a[1][2].
a[1][2].

5.  Let us see how pointer is used to access the 2-D
array.
 As we know, name of the array gives the base
address of the array i.e., address of a[0][0].
 To access a[i][j] using base pointer of the array,
 To access a[i][j] using base pointer of the array,
we can use the following generalized form:

6.  The following figure shows how the above 2-D array
will be stored in memory.
 Array elements are stored in memory row by row.

7.  In a 2-D array, each row will be considered as a one
dimensional array.
 Hence 2-D array can be considered as a collection of several
one dimensional arrays.
 In this example, each row is an array of 4 integers.
 We know that the name of an array is a constant pointer that
points to 0th row which contains address 1000.
points to 0th row which contains address 1000.

9.  Consider a two dimensional array mat[ROWS] [COLS]
where ROWS and COLS are some integer value.
 We can use any one of the following two notations to
access the two dimensional array.
 The first int mat[][COLS] is general array notation.
 Whereas int (*mat)[COLS] is a pointer to array.

11.  For passing multidimensional arrays,
First array dimension does not have to be
specified.
The second dimension must be explicitly
The second dimension must be explicitly
specified or a pointer to pointer as a parameter
to receive the address.

28.  Returning a 2D array from function is not as straight as passing
an array to a function.
 Arrays in C are passed by reference, hence any changes made to
array passed as argument persists after the function.
 So you can accept the output array you need to return, as a
parameter to the function.
parameter to the function.
 The following program demonstrates how a 2-D array is returned
from a function by passing resultant array also as a parameter.
 In the following program, main() receives two matrices as input
and these two matrices along with resultant matrix are passed as
arguments to the function sum().
 The sum() function adds the two matrices and return the
resultant matrix as result to the main() function.