Introduction to Structure in C

Posted by yanib on 2025-03-16 08:51:58 |

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A structure in C is a user-defined data type that allows you to group different types of data together under a single name. This is useful when you want to store multiple attributes (such as name, age, salary) of a person or object, but each attribute may be of different types (like string, integer, float, etc.).

Syntax to Define a Structure:

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struct structure_name {
    data_type member_variable1;
    data_type member_variable2;
    /* more members */
};

Example of a Structure:

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struct employee {
    char name[20];
    int id;
    float salary;
};

In the above example:

• struct employee is the structure definition.
• name, id, and salary are the members of the structure employee, where name is a string (char array), id is an integer, and salary is a floating-point number.

Comparison of Array and Structure

Function and Structure

Passing Structure Members to a Function

You can pass structure members to a function in C in the same way as individual variables.

Example: Passing structure members to a function:

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#include <stdio.h>
#include <conio.h>

void display(char empName[], int id, float sal) {
    printf("Name\t\tID\t\tSalary\n");
    printf("%s\t\t%d\t\t%.1f\n", empName, id, sal);
}

int main() {
    struct employee {
        char name[20];
        int id;
        float salary;
    };

    struct employee emp;

    printf("Employee Name: ");
    scanf("%s", emp.name);
    printf("Employee ID: ");
    scanf("%d", &emp.id);
    printf("Salary of the Employee: ");
    scanf("%f", &emp.salary);

    printf("The Entered Information of the Employee is:\n");
    display(emp.name, emp.id, emp.salary);

    getch();
    return 0;
}

Output:

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Employee Name: Ram
Employee ID: 100
Salary of the Employee: 15000
The Entered Information of the Employee is:
Name            ID           Salary
Ram             100          15000.0

Passing an Array of Structures to a Function

You can pass an array of structures to a function as an argument. Here's an example that works with an array of structures.

Example: Handling an Array of Structures:

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#include <stdio.h>
#include <conio.h>

#define SIZE 4

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

void display(struct student st[]) {
    printf("Student Name\t Roll\t Marks\t Remarks\n");
    for(int i = 0; i < SIZE; i++) {
        printf("%s\t\t %d\t %.2f\t %c\n", st[i].name, st[i].roll, st[i].marks, st[i].remark);
    }
}

void read(struct student stu[]) {
    for(int i = 0; i < SIZE; i++) {
        printf("Enter Information of student No %d:\n", i+1);
        printf("Name: ");
        scanf("%s", stu[i].name);
        printf("Roll: ");
        scanf("%d", &stu[i].roll);
        printf("Marks: ");
        scanf("%f", &stu[i].marks);
        printf("Remarks (P/F): ");
        stu[i].remark = getche();
        printf("\n");
    }
}

int main() {
    struct student s[SIZE];
    printf("Read information of students from user:\n");
    read(s);
    printf("\nThe Detail Information is:\n");
    display(s);

    getch();
    return 0;
}

Output:

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Read information of students from user:
Enter Information of student No 1:
Name: Hari
Roll: 101
Marks: 56
Remarks (P/F): p

Enter Information of student No 2:
Name: Bina
Roll: 102
Marks: 67
Remarks (P/F): p

Enter Information of student No 3:
Name: Gita
Roll: 103
Marks: 89
Remarks (P/F): p

Enter Information of student No 4:
Name: Krishna
Roll: 104
Marks: 12
Remarks (P/F): f

The Detail Information is:
Student Name       Roll     Marks    Remarks
Hari               101      56       p
Bina               102      67       p
Gita               103      89       p
Krishna            104      12       f

Union in C

A union is similar to a structure, but it uses the same memory location for all its members. So, only one member can hold a value at any time.

Union Example:

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#include <stdio.h>

int main() {
    union student {
        int roll;
        float marks;
    };
    
    union student st;
    
    st.roll = 455;
    printf("Roll: %d\n", st.roll);
    
    st.marks = 78.0;
    printf("Marks: %.2f\n", st.marks);
    
    return 0;
}

Output:

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Roll: 455
Marks: 78.00

In the above example:

• The union student has two members: roll and marks.
• When we assign a value to one member, it overwrites the value of the other, because both members share the same memory location.

Difference Between Structure and Union

Conclusion

• Structure allows you to store multiple different types of data together, while a union saves memory by sharing the same memory space for all its members.
• Structures are ideal when you need to store different types of data that should exist simultaneously, while unions are more memory-efficient when you only need to store one member at a time.

Let me know if you need any further clarification!