Thread: How pointer of structure store variable value

I am trying to understand How pointer of structure store variable value

This is my code

Code:

#include <stdio.h>

 struct Name 
 {
   int    account_number;  // structure member type integer
   float  balance;         // structure member type float
};


int main ()
{
	struct Name *account; //pointer to structure type struct 
	account-> account_number = 101;
	account-> balance = 10000.00;


   return 	
}

I don't understand what happens in these two lines

Code:

	account-> account_number = 101;
	account-> balance = 10000.00;

account is structure variable that point structure member type of int
account is structure variable that point structure member type of float

account is structure variable that point structure member type of int

Actually account is a pointer to a variable of type Name that is uninitialized (no memory associated to that pointer) so both of those lines produce undefined behaviour.

Is there a reason you're trying to use a pointer to a Name instead of just using a "normal" non-pointer instance?

Ie:

Code:

#include <stdio.h>
 
 struct Name 
 {
   int    account_number;  // structure member type integer
   float  balance;         // structure member type float
};
 
 
int main ()
{
    struct Name account; 
    account.account_number = 101;
    account.balance = 10000.00;
 
   return 0;
}

Perhaps you don't understand the difference between the "." normal operator and the "->" pointer operator when dealing with structures?

Originally Posted by laserlight

You forgot to set the pointer to point to an object, so what happens is that the pointer to garbage (or which happens to be a null pointer by chance) is dereferenced, possibly leading to a segmentation fault or some other undefined behaviour.

Its means if the structure variable is a pointer to structure type struct , it cannot store the value

Originally Posted by jimblumberg

Is there a reason you're trying to use a pointer to a Name instead of just using a "normal" non-pointer instance?

You are declaring a normal variable while I was declaring a pointer,

Now how we can store variable value in below code

Code:

#include <stdio.h>
 
 struct Name 
 {
   int    account_number;  // structure member type integer
   float  balance;         // structure member type float
};
 
 
int main ()
{
    struct Name *account; 
     
   return 0;
}

You first need to assign memory to that pointer, malloc() perhaps?

Originally Posted by jimblumberg

You first need to assign memory to that pointer, malloc() perhaps?

Code:

#include <stdio.h>
#include<stdlib.h>

 struct Name 
 {
   int    account_number;  // structure member type integer
   float  balance;         // structure member type float
};

int main ()
{
    struct Name *account = NULL;
    account = malloc (sizeof (*account));
    if (account !=  NULL)
    {
      account->account_number = 101;
      account->balance = 10000.00;

      printf("%d \n", account->account_number );
      printf("%f \n", account->balance );

      free(account);    // free the allocated memory
    }
    
    return 0;    
}

I don't understand what happens in these two lines

account-> account_number = 101;
account-> balance = 10000.00;

account is structure variable that point structure member type of int
account is structure variable that point structure member type of float

I don't understand what happens in these two lines

What exactly don't you understand?

account is structure variable that point structure member type of int

No account is a pointer to a struct Name, Name has two data members, account_number (an int), and balance (a float).

Do you know the difference between account.balance and account->balance? Hint one involves a normal non-pointer instance, the other a pointer instance.

Originally Posted by jimblumberg

Do you know the difference between account.balance and account->balance? Hint one involves a normal non-pointer instance, the other a pointer instance.

>account->balance?
account is pointer to structure that point structure member balance

>account.balance
account is not pointer variable that point to structure member balance

Originally Posted by jimblumberg

No account is a pointer to a struct Name, Name has two data members, account_number (an int), and balance (a float).

All are variables that hold some value. value may be integer character, memory location anything

account is variable that hold memory address of structure members