Students' Record Nested Structure C Program

#include <stdio.h>
#include <string.h>
#define SIZE 3
typedef struct Date {
    int day;
    int month;
    int year;
} dt;
typedef struct StudentName {
    char fname[50];
    char mname[50];
    char lname[50];
} stnam;
typedef struct StudentDetails {
    int roll;
    stnam nam;
    int age;
    char gender[10];
    dt dob;
    int marks[5];
    char grade[2];
} stud;
int main() {
    stud s[SIZE];
    int i = 0, total, j;
    float average;
    while (i < SIZE) {
        total = 0;  // Reset total for each student
        average = 0.0;
        puts("------------------------------------");
        printf("\n Enter details of student number:%d\n", i + 1);
        
        puts("Enter Roll Number:");
        scanf("%d", &s[i].roll);
        puts("Enter Age:");
        scanf("%d", &s[i].age);
        puts("Enter Date of Birth (day month year):");
        scanf("%d %d %d", &s[i].dob.day, &s[i].dob.month, &s[i].dob.year);
        for (j = 0; j < 5; j++) {
            printf("Enter marks of subject %d:\n", j + 1);
            scanf("%d", &s[i].marks[j]);
            total += s[i].marks[j];
        }
        average = total / 5.0;
        if (average > 90 && average <= 100) {
        strcpy(s[i].grade, "O");
        } else if (average > 80 && average <= 89) {
        strcpy(s[i].grade, "E");
        } else if (average > 70 && average <= 79) {
        strcpy(s[i].grade, "A");
        } else if (average > 60 && average <= 69) {
        strcpy(s[i].grade, "B");
        } else if (average > 50 && average <= 59) {
        strcpy(s[i].grade, "C");
        } else if (average > 40 && average <= 49) {
        strcpy(s[i].grade, "D");
        } else {
        strcpy(s[i].grade, "F");
    }
        
        puts("Enter first name:");
        scanf("%s", s[i].nam.fname);
        puts("Enter middle name:");
        scanf("%s", s[i].nam.mname);
        puts("Enter last name:");
        scanf("%s", s[i].nam.lname);
        puts("Enter Gender:");
        scanf("%s", s[i].gender);
        puts("\n------------------------------------");
        printf("\nThe entered details of student number:%d are\n", i + 1);
        printf("Roll: %d\n", s[i].roll);
        printf("Age: %d\n", s[i].age);
        printf("Date of Birth: %d/%d/%d\n", s[i].dob.day, s[i].dob.month, s[i].dob.year);
        for (j = 0; j < 5; j++) {
            printf("Entered marks of subject %d: %d\n", j + 1, s[i].marks[j]);
        }
        
        printf("Total Marks: %d\n", total);
        printf("Grade: %s\n", s[i].grade);
        printf("Name: %s %s %s\n", s[i].nam.fname, s[i].nam.mname, s[i].nam.lname);
        printf("Gender: %s\n", s[i].gender);
        puts("\n------------------------------------\n");
        i++;
    }
    return 0;
}

Explanation:-

#include <stdio.h> includes the standard input-output library for functions like printf and scanf.

#include <string.h> includes the string library for functions like strcpy.

#define SIZE 3 defines a constant SIZE that specifies the number of students. In this case, it is set to 3.

Date structure holds the day, month, and year.

StudentName structure holds the first name, middle name, and last name of a student.

StudentDetails structure holds all details about a student including roll number, name (as a StudentName structure), age, gender, date of birth (as a Date structure), marks for 5 subjects, and grade.

Main Loop Execution

• Initialization:

  • An array s of stud structures is declared to hold details of SIZE (3) students.
  • i is used to iterate over the students.
  • total and average are used to calculate and store the total marks and average marks of a student respectively.

• Input Loop:

  • The while loop runs for each student from 0 to SIZE - 1.
  • total and average are reset for each student to ensure accurate calculations.
  • Various student details are input using scanf.

• Grade Calculation:

  • Marks for 5 subjects are input and accumulated into total.
  • average is calculated by dividing total by 5.
  • Based on the average, a grade is assigned to the student by copying a grade character to s[i].grade.

• String Inputs:

  • Student's first name, middle name, last name, and gender are input using scanf.

• Output:

  •