Let us examine the following statements:
int var_x;
int* ptrX;
var_x = 6;
ptrX = &var_x;
*ptrX = 12;
printf("value of x : %d", var_x);
The first line causes the compiler to reserve a space in memory for an integer. The second line tells the compiler to reserve space to store a pointer.
A pointer is a storage location for an address. The third line should remind you the scanf statements. The address "&" operator tells compiler to go to the place it stored var_x, and then give the address of the storage location to ptrX.
The asterisk * in front of a variable tells the compiler to dereference the pointer, and go to memory. Then you can make assignments to variable stored at that location. You can reference a variable and access its data through a pointer. Let us see an example of pointers:
/* illustration of pointer use */
#include <stdio.h>
int main()
{
int index, *pt1, *pt2;
index = 39; /* any numerical value */
pt1 = &index; /* the address of index */
pt2 = pt1;
printf("The value is %d %d %d\n", index, *pt1, *pt2);
*pt1 = 13; /* this changes the value of index */
printf("The value is %d %d %d\n", index, *pt1, *pt2);
return 0;
}
The output of the program will be displayed as follows:
The value is 39 39 39
The value is 13 13 13 |
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