Hello guys, what’s up? I have found that every month people are searching about what is a structure in c. So, today I am going to discuss about it. Let’s start—

A structure is a user defined data type in C. Each element of a structure is called a member. A structure creates a data type that can be used to group items of possibly different types into a single type. Structure members can be accessed by any function, anywhere in the scope of the Structure

• Structure variable should be declared, if we want to access structure members in C,
• We can declare many structure variables for same structure & there memory will be allocated for each separately.
• If we don’t want to assign any values to structure members while declaring, It is a best practice to initialize a structure to null.

• Structure: hold group of data of different data types & Data types can be int, char, float, double and long double etc.
• Array: hold group of data of same data type.
• Normal C variable: hold only 1 data of 1 data type at a time.

Syntax of what is structure in c:

struct tag_name
{
data type var_name1;
data type var_name2;
data type var_name3;
};

Example of what is structure in c:

struct programiz
{
int  mark;
char name[10];
float average;
};

// A variable declaration with structure declaration. 
struct Point 
{ 
int x, y; 
} p1; // The variable p1 is declared with 'Point' 


// A variable declaration like basic data types 
struct Point 
{ 
int x, y; 
}; 

int main() 
{ 
struct Point p1; // The variable p1 is declared like a normal variable 
}

struct Point 
{ 
int x = 0; // COMPILER ERROR: cannot initialize members here 
int y = 0; // COMPILER ERROR: cannot initialize members here 
};

{ 
int x, y; 
}; 

int main() 
{ 
// A valid initialization. member x gets value 0 and y 
// gets value 1. The order of declaration is followed. 
struct Point p1 = {0, 1}; 
}

If you want to learn more about initializing structure in c, just click Here.

Accessing structure members using normal variable:
report.mark;
report.name;
report.average;

Accessing structure members using pointer variable:
report  -> mark;
report -> name;
report -> average;

DesignatedInitialization feature has been added in C99 standard, which allows structure members to be initialized in any order.

#include<stdio.h> 

struct Point 
{ 
int x, y, z; 
}; 

int main() 
{ 
// Examples of initializtion using designated initialization 
struct Point p1 = {.y = 0, .z = 1, .x = 2}; 
struct Point p2 = {.x = 20}; 

printf ("x = %d, y = %d, z = %dn", p1.x, p1.y, p1.z); 
printf ("x = %d", p2.x); 
return 0; 
} 

After executing above program, our output look like this:

x = 2, y = 0, z = 1
x = 20

Array of structures called as structure array in C. This is nothing but collection of structures. 

#include <stdio.h>
#include <string.h>

struct programiz
{
     int id;
     char name[30];
     float percentage;
};

int main() 
{
     int i;
     struct programiz record[2];

     // 1st programiz's record
     record[0].id=1;
     strcpy(record[0].name, "John");
     record[0].percentage = 86.5;

     // 2nd programiz's record         
     record[1].id=2;
     strcpy(record[1].name, "Himu");
     record[1].percentage = 90.5;

     // 3rd programiz's record
     record[2].id=3;
     strcpy(record[2].name, "TranVan");
     record[2].percentage = 81.5;

     for(i=0; i<3; i++)
     {
         printf("     Records of Programiz : %d n", i+1);
         printf(" Id is: %d n", record[i].id);
         printf(" Name is: %s n", record[i].name);
         printf(" Percentage is: %fnn",record[i].percentage);
     }
     return 0;
}

After executing above program, our output look like this:

Records of STUDENT : 1
Id is: 1
Name is: John
Percentage is: 86.500000
 
Records of STUDENT : 2
Id is: 2
Name is: Himu
Percentage is: 90.500000
 
Records of STUDENT : 3
Id is: 3
Name is: TranVan
Percentage is: 81.500000

If we have a pointer to structure, members are accessed using arrow ( -> ) operator.

#include<stdio.h> 

struct Point 
{ 
int x, y; 
}; 

int main() 
{ 
struct Point p1 = {1, 2}; 

// p2 is a pointer to structure p1 
struct Point *p2 = &p1; 

// Accessing structure members using structure pointer 
printf("%d %d", p2->x, p2->y); 
return 0; 
}

struct programiz {
  int local_street;
  char *town;
  char *my_city;
  char *my_country;
};
...
struct programiz var; 
var.town = "Agra";

Code using tyepdef struct c:

typedef struct programiz{
  int local_street;
  char *town;
  char *my_city;
  char *my_country;
}addr;
..
..
addr var1;
var.town = "Agra";

 If you want to learn more about typedef struct in c, just click Here.

1. Structures act as a database. C Structures can be used to store huge data.
2. C Structures can be used to send data to the printer, check computer’s memory size, clear output screen contents
3. C Structures can interact with keyboard and mouse to store the data.
4. It can be used in drawing and floppy formatting.

struct number 
{ 
 float x; 
}; 
int main() 
{ 
 struct number n1,n2,n3; 
 n1.x=4; 
 n2.x=3; 
 n3=n1+n2; 
 return 0; 
} 

/*Output: 

prog.c: In function 'main': 
prog.c:10:7: error: 
invalid operands to binary + (have 'struct number' and 'struct number') 
n3=n1+n2; 

*/

• Structures in C cannot have constructor inside Structures.
• C structures do not permit functions inside Structure 
•  C Structures cannot have static members inside their body 
• C Programming languages do not support access modifiers. So they cannot be used in C Structures. 

Today we have read many topics. Those are what is structure in c, syntax of what is a structure in c, how to declare a struct in c, initializing structure in c, arrays of structures in c, typedef struct in c and many more this. I hope today you guys have learned many more things about structures in c. So, guys, that’s all for today. Later we will discuss another tutorial on c programming.