What is pointer ?

A pointer is but a variable-like name which pointer or represents a storage location in memory (RAM). Remember that the RAM has many cells to store values. Each cell in memory is 1 byte and has a unique address to identify it.

Example :

/* Description: find a biggest number use pointer */ #include<stdio.h> main() { int a,b,*big,*xptr,*yptr; printf("\n Enter two integers : "); scanf("%d %d",&a,&b); xptr=&a; yptr=&b; if(*xptr > *yptr) big = xptr; else big = yptr; printf("\n Biggest number is %d",*big); getch(); }

Output :

pointer declaration :

a pointer is declared like a variable with appropriate data type. The pointer variable in the declaration is preceded by the *(asterisk) symbol.

Example :

int *mptr, *n;
float *xp, *yp, *zp;
char *p, *c[20]

Address Operator & :

The symbol & ( ampersand ) is an address operator which is used to access the address of a variable and assign it to a pointer to initialize it.

Example :

int m = 15, *mptr;
float x = 2.54, *xptr;

mptr = &m;
xptr = &x;

Note : The pointer maybe initialized in the declaration statement as shown below :

int m = 15, *mptr = &m;

indirection Operator * :

The symbol * ( asterisk ) is an indirection operator which is used to access the value of a variable through a pointer.

int m = 15, *mptr;
float x = 2.54, *xptr;
mptr = &m;
xptr = &x;
printf("\n Value of m = %d", *mptr);
printf("\n Value of m = %0.2f", *xptr)

When this program is executed, the values referred by the pointers are printed as shown below :

value of m = 15;
value of x = 2.54;

Note : That an address of a variable should be assigned to a pointer before the indirection operator along with the pointer is used in any manipulation.

pointer expressions :

Expression	Meaning	Result
&i	address of i	65490
&j	address of j	65492
pj	value stored in pj ( which is a pointer address )	65492
*pj	value referred by pj	65
*pi	value referred by pi	65
*pi + 2	value referred by pi + 2 = 65+2	67
*(pi - 1)	value referred in (pi - 1) (=65492 - 1*sizeof(int)=65490)	35
(pi + 2)	new value in pointer arithmetic (pi + 2) (=65492 + 2*sizeof(int)=65496)	65496
i	value of i	35
pi	value stored in pi (which is also a pointer address)	65492