Pointers :

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 :

  1. /* Description: find a biggest number use pointer */
  2. #include<stdio.h>
  3. main()
  4. {
  5. int a,b,*big,*xptr,*yptr;
  6. printf("\n Enter two integers : ");
  7. scanf("%d %d",&a,&b);
  8. xptr=&a;
  9. yptr=&b;
  10. if(*xptr > *yptr)
  11. big = xptr;
  12. else
  13. big = yptr;
  14. printf("\n Biggest number is %d",*big);
  15. getch();
  16. }

Output :

c language - find a biggest number use pointer

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 :

ExpressionMeaningResult
&iaddress of i65490
&jaddress of j65492
pjvalue stored in pj
( which is a pointer address )
65492
*pjvalue referred by pj65
*pivalue referred by pi65
*pi + 2value referred by pi + 2 = 65+267
*(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
ivalue of i35
pivalue stored in pi
(which is also a pointer address)
65492

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