Structures

Structure is the collection of variables of different types under a single name for better handling. For example: You want to store the information about person about his/her name, citizenship number and salary. You can create these information separately but, better approach will be collection of these information under single name because all these information are related to person.

Syntax of structure

struct structure_name 
{
    data_type member1;
    data_type member2;
    .
    .
    data_type memeber;
};

We can create the structure for a person as mentioned above as:

struct person
{
    char name[50];
    int cit_no;
    float salary;
};

This declaration above creates the derived data type struct person.

Structures as Function Arguments

You can pass a structure as a function argument in the same way as you pass any other variable or pointer.

#include <stdio.h>
#include <string.h>
 
struct Books {
   char  title[50];
   char  author[50];
   char  subject[100];
   int   book_id;
};

/* function declaration */
void printBook( struct Books book );

int main( ) {

   struct Books Book1;        /* Declare Book1 of type Book */
   struct Books Book2;        /* Declare Book2 of type Book */
 
   /* book 1 specification */
   strcpy( Book1.title, "C Programming");
   strcpy( Book1.author, "Nuha Ali"); 
   strcpy( Book1.subject, "C Programming Tutorial");
   Book1.book_id = 6495407;

   /* book 2 specification */
   strcpy( Book2.title, "Telecom Billing");
   strcpy( Book2.author, "Zara Ali");
   strcpy( Book2.subject, "Telecom Billing Tutorial");
   Book2.book_id = 6495700;
 
   /* print Book1 info */
   printBook( Book1 );

   /* Print Book2 info */
   printBook( Book2 );

   return 0;
}

void printBook( struct Books book ) {

   printf( "Book title : %s\n", book.title);
   printf( "Book author : %s\n", book.author);
   printf( "Book subject : %s\n", book.subject);
   printf( "Book book_id : %d\n", book.book_id);
} 

When the above code is compiled and executed, it produces the following result 

Book title : C Programming
Book author : Nuha Ali
Book subject : C Programming Tutorial
Book book_id : 6495407
Book title : Telecom Billing
Book author : Zara Ali
Book subject : Telecom Billing Tutorial
Book book_id : 6495700

Example program for array of structures in C

This program is used to store and access “id, name and percentage” for 3 students. Structure array is used in this program to store and display records for many students. You can store “n” number of students record by declaring structure variable as ‘struct student record[n]“, where n can be 1000 or 5000 etc.

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

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

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

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

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

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

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

Output:



Records of STUDENT : 1
Id is: 1
Name is: Raju
Percentage is: 86.500000



Records of STUDENT : 2
Id is: 2
Name is: Surendren
Percentage is: 90.500000



Records of STUDENT : 3
Id is: 3
Name is: Thiyagu
Percentage is: 81.500000

Example program for declaring many structure variable in C

In this program, two structure variables “record1″ and “record2″ are declared for same structure and different values are assigned for both structure variables. Separate memory is allocated for both structure variables to store the data.

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

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

int main() 
{
     int i;
     struct student record1 = {1, "Raju", 90.5};
     struct student record2 = {2, "Mani", 93.5};

     printf("Records of STUDENT1: \n");
     printf("  Id is: %d \n", record1.id);
     printf("  Name is: %s \n", record1.name);
     printf("  Percentage is: %f \n\n", record1.percentage);

     printf("Records of STUDENT2: \n");
     printf("  Id is: %d \n", record2.id);
     printf("  Name is: %s \n", record2.name);
     printf("  Percentage is: %f \n\n", record2.percentage);

     return 0;
}

Output:

Records of STUDENT1: Id is: 1 Name is: Raju Percentage is: 90.500000 Records of STUDENT2: Id is: 2 Name is: Mani Percentage is: 93.500000