Structures in C Programming

Structure is a collection of heterogeneous (i.e. of different types) data items which are referenced by a single name.

Structure is also known as record. A structure is a convenient way of grouping several data items together.

In C programming language, using structure, we can create and use data types other than the basic or fundamental data types. These are known as user defined data types. Structures are created by using struct keyword and can be defined as user defined data types.

Declaration of Structure & Structure Variables

Syntax for Declaring Structure


struct structure_name
{
 data_type member1;
 data_type member2;
 data_type member3;
  .
  .
  .
 data_type memberN;
};

Where structure_name and member can be any valid C identifier, data type can be any valid C data types. Structure name is also known as tag. When we declare a structure, new data type is defined. After declaring structure, structure variables can be created by using keyword struct and structure_name.

Syntax for Creating Structure Variables After Declaring Structure


struct structure_name  var1, var2, var3, …., varN;

Example: Declaration & Creation of Structure Variables

Let's create structure named student with member name, roll & marks:


struct  student
{
 char  name[30];
 int  roll;
 float  marks;
};

In this example, student is name of structure and it has three members, namely, name, roll and marks. Now struct student is name of new data type which can be used to create new structure variables.

For Example:


struct student  s1, s2, s3;

In the above example s1, s2, s3 are structure variables.

Structure variables can also be created at the time of structure declaration.

General syntax for declaring structure variables at the time of structure declaration is:


struct  structure_name
{
 data_type member1;
 data_type member2;
 data_type member3;
  .
  .
  .
 data_type memberN;
 
} var1, var2, var3, …., varN;

For Example


struct student
{
 char  name[30];
 int  roll;
 float  marks;
}s1, s2, s3;

Initialization of Structure Variables

Assigning value to the structure variable at the time declaration of structure variable is known as initialization of structure variables. Structure variables can be initialized by using the notation used for array initialization i.e. using {value 1, value 2, ..., value N}.

Example: Initialization of Structure Variables

If structure is declared like this:


struct student
{
  char  name[30];
  int  roll;
  float  marks;
};

Then structure variables can be created and initialized like this:


struct student s1 = {“Parijat”, 13, 80.5};
struct student s2 = {“Suyogbir”, 17, 60};
struct student s3 = {“Sakambari”, 19, 50.5};

Accessing Structure Elements

Individual structure elements can be accessed by using the . (dot) operator along with structure variables.

The general syntax for accessing structure variables is:

structure_variable.member_name

Example: Accessing Structure Elements

If structure is declared like this:


struct student
{
  char  name[30];
  int  roll;
  float  marks;
};

And, structure variables are created and initialized like this:


struct student s1 = {“Parijat”, 13, 80.5};
struct student s2 = {“Suyogbir”, 17, 60};
struct student s3 = {“Sakambari”, 19, 50.5};

Then, individual value can be obtained as:

s1.name gives  “Parijat”
s1.roll gives 13
s1.marks gives 80.5

similarly,

s2.name gives “Suyogbir”
s2.roll gives 17
s2.marks gives 60

Structure Examples

So far so good! Now let's look at the complete C program for structures.

Example 1: C program to illustrate declaration and initialization of structure


#include<stdio.h>

/* Declaration of structure */
struct student
{
 char name[30];
 int roll;
 float marks;
};

int main()
{
 /* Declaration and initialization of structure variable */ 
 struct student s1 = {"Parijat", 17, 80.5};
 
 printf("Student detail is:\n");
 printf("Name : %s\n", s1.name);
 printf("Roll : %d\n", s1.roll);
 printf("Marks : %f\n", s1.marks);
 
 return 0;
}

The output of the above program is:

Student detail is:
Name : Parijat
Roll  : 17
Marks : 80.500000

Example 2: C program to illustrate reading data in structure variables and displaying the content


#include<stdio.h>

/* Declaration of structure */
struct student
{
 char name[30];
 int roll;
 float marks;
};

int main()
{
 /* Declaration of structure variable */
 struct student s1;
 
 printf("Enter name, roll and marks of student:\n");
 scanf("%s%d%f",s1.name, &s1.roll, &s1.marks);
 printf("Student detail is:\n");
 printf("Name : %s\n", s1.name);
 printf("Roll : %d\n", s1.roll);
 printf("Marks : %f\n", s1.marks);
 
 return 0;
}