Pointer to Array in C
Pointer to
Array in C
Pointer to
array is a pointer variable that points to an array. It is also known as array
pointer for short. It is usually used to reference that rows of a two
dimensional array as each row of two dimensional array is an array itself.
Pointer to
array means we can declare a pointer variable that can point to the whole array
instead of one element of the array.
Its Syntax is,
data_type
(*arrptr) [MAX_elements_in_row];
Where
arrptr is the name of the pointer variable which will be pointing to value of
type data_type and MAX_elements_in_row is a
positive-valued integer expression that indicates the maximum number of
elements in each row of the two dimensional array.
In the above declaration, we notice that the
pointer type (the asterisk) is placed within parentheses because of precedence.
The brackets [] have greater
precedence that the asterisk (*).
Without the parentheses to force precedence, brackets would be evaluated first.
So you would have array of pointers instead of pointer to an array.
The statement,
int (*rowptr) [4];
declares a
pointer to an array of 4 elements with type int.
  value |
of
|
Int
|
type
|
Pointer to
array containing 4 elements
Once we
assign the address of an appropriate array to pointer to an array then the
expression (*rowptr) yields the
array and (*rowptr) [i] yields the array element at index
i.
Consider
the following program.
C program to
show how array elements are accessed using pointer to array
#include
<stdio.h>
#include
<conio.h>
void main
()
{
int a[3]
[4] = {{3, 4, 5, 6}, (10, 20, 30, 40}, {1, 4, 3, 9}};
int
(*rowptr) [4] ; /* pointer to array
of 4 elements with type int */
int *ptr;
clrscr ();
rowptr =
a; /* Stores the address of
first element */
printf (“-
- - - - Elements are - - - - -\n”);
while
(rowptr<(a+3)) /* As 3 rows */
{
ptr =
*rowptr; /* Stores address of first
element of each row */
printf (“Row
address = %u\n”,ptr);
printf (“Elements
of this row - - - - :”);
while
(ptr<(*rowptr+4)) /*As 4 elements in
each row */
{
printf (“%d\t”,
*(ptr));
ptr++; /* Makes ptr point to next element in each
row */
}
rowptr++; /*Makes rowptr point to element after 4
elements */
printf (“\n”);
}
getch ();
}
OUTPUT
- - - - -
Elements are - - - - -
Row address
= 65466
Elements of
this row - - - - : 3 4 5
6
row address
= 65474
Elements of
this row - - - - : 10 20 30
40
Row address
= 65482
Elements of
this row - - - - : 1 4 3
9
Explanation: In this program, the statement
int
(*rowptr) [4];
declares a
pointer to an array of 4 elements with type int.
The
statement, rowptr = a; stores the address of first element of array a.
Some other
Example (Program):
Example of
pointer to one dimensional array.
#include
<stdio.h>
#include
<conio.h>
void main
()
{
int x;
int n[5] =
{10, 20, 30, 40, 50);
int *p =
m; /* or int *ptr = &m[0] */
for (x=0;
x<5; x++)
{
printf (“%d\t”
, *p);
p++;
}
getch ();
}
OUTPUT
10 20
30 40
Example of
pointer to two dimensional arrays.
#include
<stdio.h>
#include
<conio.h>
void main
()
{
int x, y;
int m[2]
[2] = { { 10, 20}, {30, 40} };
int (*p)
[2] = m;
for (x=0;
x<2; x++)
{
for (y=0;
y<2; y++)
printf (“%d\t”,
(*(p+x) ) [y] );
}
getch ();
}
OUTPUT
10 20
30 40
Leave a Comment