Write a C program to display the size and offset of structure members

Problem

Write a C program to define the structure and display the size and offsets of member variables

Structure − It is a collection of different datatype variables, grouped together under a single name.

General form of structure declaration

datatype member1;
struct tagname{
   datatype member2;
   datatype member n;
};

Here, struct  - keyword

tagname - specifies name of structure

member1, member2 - specifies the data items that make up structure.

Example

struct book{
   int pages;
   char author [30];
   float price;
};

Structure variables

There are three ways of declaring structure variables −

Method 1

struct book{
   int pages;
   char author[30];
   float price;
}b;

Method 2

struct{
   int pages;
   char author[30];
   float price;
}b;

Method 3

struct book{
   int pages;
   char author[30];
   float price;
};
struct book b;

Initialization and accessing of structures

The link between a member and a structure variable is established using the member operator (or) dot operator.

Initialization can be done in the following ways −

Method 1

struct book{
   int pages;
   char author[30];
   float price;
} b = {100, "balu", 325.75};

Method 2

struct book{
   int pages;
   char author[30];
   float price;
};
struct book b = {100, "balu", 325.75};

Method 3 (using member operator)

struct book{
   int pages;
   char author[30];
   float price;
} ;
struct book b;
b. pages = 100;
strcpy (b.author, "balu");
b.price = 325.75;

Method 4 (using scanf function)

struct book{
   int pages;
   char author[30];
   float price;
} ;
struct book b;
   scanf ("%d", &b.pages);
   scanf ("%s", b.author);
   scanf ("%f", &b. price);

Declare the structure with data members and try to print their offset values as well as size of the structure.

Program

#include<stdio.h>
#include<stddef.h>
struct tutorial{
   int a;
   int b;
   char c[4];
   float d;
   double e;
};
int main(){
   struct tutorial t1;
   printf("the size 'a' is :%d\n",sizeof(t1.a));
   printf("the size 'b' is :%d\n",sizeof(t1.b));
   printf("the size 'c' is :%d\n",sizeof(t1.c));
   printf("the size 'd' is :%d\n",sizeof(t1.d));
   printf("the size 'e' is :%d\n",sizeof(t1.e));
   printf("the offset 'a' is :%d\n",offsetof(struct tutorial,a));
   printf("the offset 'b' is :%d\n",offsetof(struct tutorial,b));
   printf("the offset 'c' is :%d\n",offsetof(struct tutorial,c));
   printf("the offset 'd' is :%d\n",offsetof(struct tutorial,d));
   printf("the offset 'e' is :%d\n\n",offsetof(struct tutorial,e));
   printf("size of the structure tutorial is :%d",sizeof(t1));
   return 0;
}

Output

the size 'a' is :4
the size 'b' is :4
the size 'c' is :4
the size 'd' is :4
the size 'e' is :8
the offset 'a' is :0
the offset 'b' is :4
the offset 'c' is :8
the offset 'd' is :12
the offset 'e' is :16

size of the structure tutorial is :24