Pointers and Structures

POINTERS AND STRUCTURES

Pointer pointing to a structure is known as structure pointers

struct

{

   member 1;

   member2;

} variable, *ptr;

Here, the variable represents structure type variable and *ptr represents the name of the pointer.

Example 1: Program to declare pointer to structure and display the contents of the structure.

/* Program to print name, place and account number */

#include <stdio.h>

#include<conio.h>

void main()   * Local definitions */

{.

struct account

{

      char name[20];

      char place[25];

      int acctno;

};

static struct account_m4={"Venkat", "Arcot", 24201};

struct account *ptr;

/* Statements */

clrscr();

ptr=&m4;

printf("%s\t%s\t%d\n", m4.name, m4.place, m4.acctno);

printf("%s\t%s\t%d\n", ptr‒>name,ptr‒>place,ptr‒> acctno);

getch();

} /* main */

OUTPUT

Venkat Arcot 24201

Venkat Arcot 24201

EXPLANATION: In the above program, the function printf() statement prints the structure elements by calling them as usual. The second printf() statement prints the structure element using pointer and arrow operator is used instead of dot (.) operator.

Here, ptr is not a structure variable, dot operator cannot be used. C language provides an arrow operator '→' to refer the structure elements.

operator '→' is always a pointer to a structure.

Example 2: Program to print name, place and account number using structure and pointer.

/* Program using structures and pointers */

/* account is a structure name with character string and integer variable # */

include <stdio.h>

struct account

{

     char name[20];

     char place [25];

     int acctno;

};

main()

{

      /* Local definitions */

      static struct account m4={"madhavan", "Chennai", 241};

      display (&m4);  /* function call */

} /* main */

display(m) /* display() is a function */

struct account a; /* pointer to a structure*/

{

        prinf ("%s\n%s\n%d\n", ptr‒>name, ptr‒>place, ptr‒> acctno); }

} /* display */

OUTPUT

Madhavan

Chennai

241

EXPLANATION: In the above program, struct account is declared with members name, place of character type and acctno of integer type. In the main function, the structure account is declared as static type. The user defined function display() is called, then the control is transferred to user defined function display(). The display function access the structure account and print the name, place and acctno. Here the structure struct account is declared outside the function main() so that the data is available to the function display( ).

Naturally, a pointer also can be a member of a structure.

Syntax:

struct int_pointers

{

        int *p1;

        int *p2;

}

Description:

In this definition, a structure called into pointer is defined to contain two integer pointers p1 and p2.