K. J.
Somaiya School of Engineering, Mumbai-77
(Somaiya Vidyavihar University)
Department of Science and Humanities
Course Name: Programming in C Semester: II
Date of
___ / ___ / ______ DIV/ Batch No:
Performance:
Student Name: Roll No:
Experiment No: 7
Title: Structures and unions
Aim and Objective of the Experiment:
Write a program in C to demonstrate use of structures and unions.
COs to be achieved:
CO4: Design modular programs using functions and the use of structure and union.
Theory:
Introduction to Structures
A structure is a user-defined data type in C that groups variables of different types under a single
name. Structures are used when you need to store multiple related pieces of data, such as
information about a student, employee, or product, where each field might have a different data
type (e.g., integers, floats, and characters).
Example: A structure could be defined to store a student's name, age, and grade.
Declaring and Defining a Structure
To declare and define a structure in C, you first use the struct keyword, followed by a structure
name, and the members enclosed within curly braces {}. Each member can be of a different data
type.
Programming in C Semester: II Academic Year: 2024-25
K. J. Somaiya School of Engineering, Mumbai-77
(Somaiya Vidyavihar University)
Department of Science and Humanities
Syntax:
struct structure_name {
data_type member1;
data_type member2;
// more members
};
Example:
struct Student {
char name[50];
int age;
float grade;
};
This defines a structure Student with three members: a string for the name, an integer for the age,
and a float for the grade.
Structure Initialization
Structures can be initialized at the time of declaration or later by assigning values to their members
individually. If initialization during declaration, values for the members are assigned in the same
order as their declaration.
Syntax for initialization:
struct structure_name variable_name = {value1, value2, ...};
Programming in C Semester: II Academic Year: 2024-25
K. J. Somaiya School of Engineering, Mumbai-77
(Somaiya Vidyavihar University)
Department of Science and Humanities
Example:
struct Student student1 = {"John", 20, 85.5};
Alternatively, individual members can be initialized after declaration:
student1.age = 21;
strcpy(student1.name, "Alice");
student1.grade = 90.0;
Accessing and Displaying Structure Members
Structure members can be accessed using the dot (.) operator. The member values can be printed or
manipulated as required.
Syntax:
variable_name.member_name
Example:
printf("Name: %s\n", student1.name);
printf("Age: %d\n", student1.age);
printf("Grade: %.2f\n", student1.grade);
If a structure is pointed to by a pointer, the arrow (->) operator is used to access members.
Programming in C Semester: II Academic Year: 2024-25
K. J. Somaiya School of Engineering, Mumbai-77
(Somaiya Vidyavihar University)
Department of Science and Humanities
Example:
struct Student *ptr = &student1;
printf("Name: %s\n", ptr->name);
Array of Structures
An array of structures is used when you want to store multiple instances of a structure. Each
element of the array is a structure.
Syntax: struct structure_name array_name[size];
Example:
struct Student students[3];
students[0].age = 20;
strcpy(students[0].name, "Alice");
students[0].grade = 90.0;
To loop through an array of structures, you can use a for loop:
for (int i = 0; i < 3; i++) {
printf("Name: %s, Age: %d, Grade: %.2f\n", students[i].name, students[i].age,
students[i].grade);
Introduction to Unions
Programming in C Semester: II Academic Year: 2024-25
K. J. Somaiya School of Engineering, Mumbai-77
(Somaiya Vidyavihar University)
Department of Science and Humanities
A union is a user-defined data type similar to a structure, but with one key difference: all members
of a union share the same memory location. This means that at any given time, only one member of
the union can hold a value, making it more memory efficient when you don't need to store multiple
values simultaneously.
Syntax:
union union_name {
data_type member1;
data_type member2;
// more members
};
Example:
union Data {
int i;
float f;
char str[20];
};
In the above example, the Data union can store an integer, a float, or a string, but only one of these
at a time. The memory allocated for all the members of the union is the size of the largest member.
Accessing Members of a Union
Just like structures, union members are accessed using the dot (.) operator. However, because all
members share the same memory space, modifying one member will overwrite the other members'
Programming in C Semester: II Academic Year: 2024-25
K. J. Somaiya School of Engineering, Mumbai-77
(Somaiya Vidyavihar University)
Department of Science and Humanities
values.
Example:
union Data data;
data.i = 10; // Valid
data.f = 3.14; // Overwrites 'i'
data.str = "Hello"; // Overwrites 'f'
Problem Statements:
Design a C program to manage employee data using structures and unions. The program should
allow the following functionalities:
1. Employee Data Input:
o Each employee should have the following common attributes:
▪ Employee ID (integer)
▪ Name (string)
▪ Age (integer)
▪ Department (string)
▪ Basic Salary (float)
o Depending on the employee's role, additional attributes should be stored:
Programming in C Semester: II Academic Year: 2024-25
K. J. Somaiya School of Engineering, Mumbai-77
(Somaiya Vidyavihar University)
Department of Science and Humanities
▪ For Sales Employees:
▪ Commission (float)
▪ Sales Target (float)
▪ For Technical Employees:
▪ Project Name (string)
▪ Project Allowance (float)
o Use a union to store role-specific data efficiently.
2. Employee Data Display:
o Display all employee details, including role-specific information, in a formatted
manner.
3. Calculate Total Salary:
o For each employee, calculate the total salary based on their role:
▪ For Sales Employees: Total Salary = Basic Salary + Commission
▪ For Technical Employees: Total Salary = Basic Salary + Project Allowance
4. Search Employee by ID:
o Allow the user to search for an employee by their Employee ID and display their
details.
5. Update Employee Data:
o Allow the user to update specific details of an employee (e.g., name, age,
department, or role-specific data).
6. Delete Employee Data:
Programming in C Semester: II Academic Year: 2024-25
K. J. Somaiya School of Engineering, Mumbai-77
(Somaiya Vidyavihar University)
Department of Science and Humanities
o Allow the user to delete an employee's record by their Employee ID.
Requirements:
1. Use a structure to represent an employee with common attributes.
2. Use a union to store role-specific attributes (either for sales or technical employees).
3. Use an enum to differentiate between employee roles (e.g., SALES, TECHNICAL).
4. Implement dynamic memory allocation to store employee records.
5. Provide a menu-driven interface for the user to perform the above operations.
Code :
Output:
Post Lab Subjective/Objective type Questions:
1. What is the difference between a structure and a union in C?
Conclusion:
Programming in C Semester: II Academic Year: 2024-25
K. J. Somaiya School of Engineering, Mumbai-77
(Somaiya Vidyavihar University)
Department of Science and Humanities
Signature of faculty in-charge with Date:
Programming in C Semester: II Academic Year: 2024-25
