Student Marks Using Structures in C

Algorithm

1. Define struct Student with a name and a float marks field.
2. Read N and then the name and marks of each student into an array of structures.
3. Add up the marks and divide by N to get the average.
4. Print every student whose marks are greater than the average under an 'above average' heading.
5. Print every student whose marks are less than the average under a 'below average' heading; a student equal to the average appears in neither list.

C program

#include <stdio.h>

#define MAX_STUDENTS 50

struct Student {
    char name[30];
    float marks;
};

int main(void) {
    struct Student list[MAX_STUDENTS];
    int n, i, count_above, count_below;
    float total = 0.0f, average;

    printf("Enter number of students (1-%d):\n", MAX_STUDENTS);
    if (scanf("%d", &n) != 1 || n < 1 || n > MAX_STUDENTS) {
        printf("Error: invalid number of students\n");
        return 1;
    }

    for (i = 0; i < n; i++) {
        printf("Student %d name and marks:\n", i + 1);
        scanf("%29s %f", list[i].name, &list[i].marks);
        total += list[i].marks;
    }

    average = total / n;
    printf("Average marks: %.2f\n", average);

    count_above = 0;
    printf("Students above average:\n");
    for (i = 0; i < n; i++) {
        if (list[i].marks > average) {
            printf("  %s - %.2f\n", list[i].name, list[i].marks);
            count_above++;
        }
    }
    if (count_above == 0) {
        printf("  None\n");
    }

    count_below = 0;
    printf("Students below average:\n");
    for (i = 0; i < n; i++) {
        if (list[i].marks < average) {
            printf("  %s - %.2f\n", list[i].name, list[i].marks);
            count_below++;
        }
    }
    if (count_below == 0) {
        printf("  None\n");
    }
    return 0;
}

Sample input and output

5
Asha 78
Ravi 65
Meena 90
Kiran 65
Divya 82

Enter number of students (1-50):
Student 1 name and marks:
Student 2 name and marks:
Student 3 name and marks:
Student 4 name and marks:
Student 5 name and marks:
Average marks: 76.00
Students above average:
  Asha - 78.00
  Meena - 90.00
  Divya - 82.00
Students below average:
  Ravi - 65.00
  Kiran - 65.00

2
Anu 50
Bala 50

Enter number of students (1-50):
Student 1 name and marks:
Student 2 name and marks:
Average marks: 50.00
Students above average:
  None
Students below average:
  None

How the program works

An array of struct Student keeps each student's name and marks together, so the average and the two lists are computed by walking one array instead of parallel arrays that can drift out of step.

The total is accumulated in a float and divided once at the end. A student whose marks equal the average is excluded from both lists, so the program never reports someone as both above and below.

Viva questions

Common mistakes

• Using the array size instead of the number of students in the average.
• Reading names with scanf("%s") without a width, which can overflow the field.
• Treating a student with marks equal to the average as above or below it.