STRUCTURE
A structure is user-defined data type that can hold multiple data of the same data types or varying data types. The data items in a structure are referred to as a member or element of the structure.
For eg: student_id, name, phone_number, marks_scored can be members of a structure.
DECLARATION OF STRUCTURE AND STRUCTURE VARIABLES
Structure can be declared with ‘struct’ keyword. The struct statement defins a new data type with more than one member.
Syntax for declaring a structure
Struct structure_name
{
Data_type member_variable1;
Data_type member_variable2;
……………………………………………..
Data_type member_variable n;
};
Eg:
Struct employee
{
Int emp_id;
Char name[20];
Char add[20];
Float sal;
}em1, em2, em3;
Accessing member of structure
The member of a structure can be accessed using period (.) sign between the structure variable and the member.
Syntax
Structure_variable.member
Eg:
#include<stdio.h>
Struct student
{
Int roll;
Char name[20];
Char add[20];
}
St;
Void main()
{
Printf(“enter name:”);
Scanf(“%s”, &st.name);
Printf(“enter roll no:”);
Scanf(“%s”, &st.roll);
Printf(“enter address:”);
Scanf(“%s”, &st.add);
Printf(“name=%s, rollno=%d, address=%s”, st.name, st.roll, st.add); }
Nested structure
Nested structure in C refers to a structure within a structure. The structure provides a convenient way to declare structure as a member of another structure.
Syntax:
Struct structure_name1
{
Data_type member1;
Data_type member2;
………………………………..
Data_type member n;
}
The above structure ‘structure_name1’ can be nested within another structure struct structure_name2
{
Data_type member1;
Data_type member2;
………………………………..
Struct structure_name1 structure_variable1;
} structure_variable2;
ACCESSING MEMBERS OF A STRUCTURE IN A NESTED STRUCTURE
The members of a structure ‘adders’ can accessed by;
Emp.add.city
Emp.add.street
Emp.add.phone
But the members within ‘employee’ can be accessed as usual.
Emp.name
Emp.emp_id
Eg:
#include <stdio.h>
struct FirstName {
char first[20];
};
struct LastName {
char last[20];
};
struct FullName {
struct FirstName first_name;
struct LastName last_name;
};
int main()
{
struct FullName name;
printf(“Enter your first name: “);
scanf(“%s”, name.first_name.first);
printf(“Enter your last name: “);
printf(“Your full name is: %s %s\n”, name.first_name.first, name.last_name.last);
return 0;
}
ARRAR OF STRUCTURE
The structure provides a convenient way of creating its array. Similar to the array we create for other data types, the structure array can also by created.
| Roll name add | Roll name add | Roll name add | ……………………….. | Roll name add |
| St[0] | st[1] | st[2] | st[3] | st[4] |
The members of an array cn be accessed as:
St[0].roll, st[0].name, st[0].add, and so on.
Eg:
#include <stdio.h>
#include <string.h>
struct Person
{
char name[MAX_NAME_LENGTH];
};
int main()
{
struct Person people[MAX_PEOPLE];
int num_people;
printf(“Enter the number of people: “);
scanf(“%d”, &num_people);
for (int i = 0; i < num_people; i++)
{
printf(“Enter name for person %d: “, i+1);
scanf(“%s”, people[i].name);
}
printf(“\nNames entered:\n”);
for (int i = 0; i < num_people; i++)
{
printf(“Person %d: %s\n”, i+1, people[i].name);
}
return 0;
}
UNION
A union is similar to a structure. Like structure, a union is also a user-defined data type that can hold multiple data of the same data types or varying data types.
For eg: student_id, name, phone_number, marks_scored can be members os a structure.
DECLARATION OF UNION AND UNION VARIABLE
Union keyword is used to declare a union. The union statements defines a new data type with more than one member.
Syntax for declaring a union
Union union_name
{
Data_type member_variable1;
Data_type member_variable2;
………………………………………………
Data_type member_variable n;
};
Eg:
#include <stdio.h>
#include <string.h>
union Name
{
char firstName[20];
char lastName[20];
};
int main()
{
union Name name;
printf(“Enter your first name: “);
scanf(“%s”, name.firstName);
printf(“Your first name is: %s\n”, name.firstName);
printf(“Enter your last name: “);
scanf(“%s”, name.lastName);
printf(“Your last name is: %s\n”, name.lastName);
return 0;
}
Similar to structure, the union variable of a union student can be declared as union st;
If you have to declare multiple union variables then, it can be declared as union student st1, st2, st3; Here, st1, st2, and st3 are the union variables that can be used to access the members.
We also have a way of combining union definition and its variable.
#include <stdio.h>
#include <string.h>
union Data
{
char name[50];
int id;
};
int main()
{
union Data data;
printf(“Enter a name: “);
scanf(“%s”, data.name);
printf(“Name: %s\n”, data.name);
return 0;
}
ACCESSING MEMBER OF UNION
The member of a union can be accessed using period (.) sign between the union variable and the member.
Syntax:
Union_variable.member
Eg:
#include <stdio.h>
#include <string.h>
union Name
{
char firstName[20];
char lastName[20];
};
int main() {
union Name name;
printf(“Enter first name: “);
scanf(“%s”, name.firstName);
printf(“Enter last name: “);
scanf(“%s”, name.lastName);
printf(“Full name: %s %s\n”, name.firstName, name.lastName);
return 0;
}
Different between structure and union
| STRUCTURE | UNION |
| Struct keyword is used to define a structure. | Union keyword is used to define a union. |
| Each member of structure has dedicated | All the members of union share a single or |
| memory address. Thus, a structure variable | common memory addresses. Thus, a union |
| occupies more memory than that of the union. | variable occupies less memory than that of a |
| structure. | |
| The size of memory required to store a structure | The size of memory required to store a union |
| variable is the sum of the sizes of the memory | variable is same as the member that occupies |
| required for each members. | the largest memory. |
| All the members can be accessed at a time. | Only one member can be accessed at a time. |
| Syntax: | Syntax: |
| Struct structure_name | Union union_name |
| { | { |
| Data_type member_variable1; | Data_type member_variable1; |
| Data_type member_variable2; | Data_type member_variable2; |
| ……………………………………………… | …………………………………………………. |
| Data_type member_variable n; | Data_type member_variable n; |
| }st; | }un: |