Pointers:

A pointer is a variable whose value is a memory address. A pointer contains the memory address of a variable that, in turn, contains a specific value. In this sense, a variable name directly references a value, and a pointer indirectly references a value.

Syntax:

type * variable ;

Interpretation:

The value of the pointer variable ptr is a memory address. A data item whose address is stored in this variable must be of the specified type.

Dynamic Memory Management:

C/C++ enables programmers to control the allocation and deallocation of memory in a program for any built in or user defined type.
The ability for a program to obtain more memory space at execution time to hold new nodes, and to release space no longer needed is known as dynamic memory management.

Syntax:

int *num = (int *)malloc(sizeof (int)*numCount);
or
int *ptr = (int *)calloc(numCount, sizeof (int));
/* returns a pointer to a section of memory just large enough to hold the integers, whose quantity is being obtained through user input stored in the variable numCount. */
free(ptr);     //returns to the system whatever memory was pointed to by ptr.

POINTER TO POINTER(Double Pointer) DECLARATION:

Syntax:

type ** variable ;

Interpretation:

The value of the pointer variable ptr2ptr is a memory address of another pointer.

Implementation of Pointers in C:

#include <stdio.h>
#include<malloc.h>

int main()
{

int row,col,x,y;

printf(“Enter number of rows:”);

scanf(“%d”,&row);

printf(“Enter number of columns:”);

scanf(“%d”,&col); //allocate memory for xs

int **ptr = (int **)calloc(row, sizeof (int*));

//for each x allocate memory for yumns

for(x=0;x<row;x++)

*(ptr+x) = calloc(col,sizeof(int)); //Storing elements

for (x=0;x<row;x++)

for(y=0;y<col;y++)

{
printf(“Enter number: “);

scanf(“%d”,&ptr[x][y]);

}

//Displaying pointer to pointer to ptr

printf(“nYou have entered:n”);

for (x=0;x<row;x++)
{
for(y=0;y<col;y++)
{
printf(“%d “,ptr[x][y]);
}
printf(“n”);
}

free(ptr);
//returns to the system whatever memory was pointed to by ptr.

return 0;
}