Grade of Mark in C program

#include <stdio.h>
int main(void){
    int num;  // Declare a variable to store the input
    
    printf("Enter your mark ");  // Prompt the user to enter their mark
    scanf("%d", &num);  // Read the user input
    
    printf(" You entered %d \n", num);  // Print the entered mark
    
    if(num >= 80){
        printf(" You got A grade");  // Check for A grade
    }
    else if (num >= 60){  // Check for B grade
        printf(" You got B grade");
    }
    else if (num >= 40){  // Check for C grade
        printf(" You got C grade");
    }
    else {  // Check for failing condition
        printf(" You Failed in this exam");
    }
    return 0;  // End of program
}

Not allowing mark above 100

#include <stdio.h>
int main(void){
    int num;  // Declare a variable to store the input
    
    printf("Enter your mark ");  // Prompt the user to enter their mark
    scanf("%d", &num);  // Read the user input
    
    printf(" You entered %d", num);  // Print the entered mark
    
    if (num > 100) {  // Check for invalid marks greater than 100
        printf(" ! Wrong data ");
    }
    else if (num >= 80) {  // Check for A grade
        printf(" You got A grade");
    }
    else if (num >= 60) {  // Check for B grade
        printf(" You got B grade");
    }
    else if (num >= 40) {  // Check for C grade
        printf(" You got C grade");
    }
    else {  // Check for failing condition
        printf(" You Failed in this exam");
    }
    return 0;  // End of program
}

Calculating Percentage ,Average and Grade

#include <stdio.h>

void main() {
    float m1, m2, m3;  // Variables for marks
    float per, avg;  // Variables for percentage and average
    float total;  // Variable for total marks
    
    printf(" enter the marks of m1 ");
    scanf("%f", &m1);  // Input for m1
    
    printf(" enter the marks of m2 ");
    scanf("%f", &m2);  // Input for m2
    
    printf("enter the marks of m3 ");
    scanf("%f", &m3);  // Input for m3
    
    total = m1 + m2 + m3;  // Calculate total marks
    printf("\n the total mark is %.2f ", total);  // Display total
    
    per = (total / 300) * 100;  // Calculate percentage
    avg = (total / 3);  // Calculate average
    printf("\n the percentage mark is : %.2f ", per);  // Display percentage
    printf("\n the average mark  is: %.2f", avg);  // Display average
    
    // Grade calculation
    if(per >= 80) printf("\n Grade : A");
    else if(per >= 60) printf("\n Grade : B");
    else if(per >= 40) printf("\n Grade : C");
    else printf("\n Fail ");  // Grade calculation based on percentage
    
    printf("\n Press Enter to exit...");
    getchar();  // Wait for user input before exiting
}

Example 2: Calculating Grades for Multiple Students Using Arrays

To calculate grades for multiple students, you can use arrays to store their marks and loop through them:

#include <stdio.h>

int main() {
    int marks[5] = {85, 92, 75, 60, 45};  // Array of student marks
    char grade;  // Variable to store the grade
    
    for (int i = 0; i < 5; i++) {  // Loop through each student
        if (marks[i] >= 90) {  // Grade A for marks 90 or above
            grade = 'A';
        } else if (marks[i] >= 80) {  // Grade B for marks 80-89
            grade = 'B';
        } else if (marks[i] >= 70) {  // Grade C for marks 70-79
            grade = 'C';
        } else if (marks[i] >= 60) {  // Grade D for marks 60-69
            grade = 'D';
        } else {  // Grade F for marks below 60
            grade = 'F';
        }
        printf("Student %d: Marks = %d, Grade = %c\n", i + 1, marks[i], grade);  // Display student info
    }
    return 0;  // Exit the program
}

Example 3: Calculating Average Grade of the Class

This example calculates the average marks and assigns a grade based on the overall class performance:

#include <stdio.h>

int main() {
    int marks[5] = {85, 92, 75, 60, 45};  // Array of student marks
    int total = 0;  // Variable to store the total marks
    float average;  // Variable to store the class average
    char grade;  // Variable to store the class grade
    
    for (int i = 0; i < 5; i++) {  // Loop through the marks array
        total += marks[i];  // Add each student's marks to the total
    }
    average = total / 5.0;  // Calculate the class average

    // Assign the grade based on the average
    if (average >= 90) {
        grade = 'A';
    } else if (average >= 80) {
        grade = 'B';
    } else if (average >= 70) {
        grade = 'C';
    } else if (average >= 60) {
        grade = 'D';
    } else {
        grade = 'F';
    }

    printf("Class Average = %.2f, Grade = %c\n", average, grade);  // Print the results

    return 0;  // End of the program
}

Example 4: Handling Invalid Input

Here’s how to handle invalid input where marks might be out of the valid range (0-100):

#include <stdio.h>

int main() {
    int mark;  // Variable to store the student's mark
    printf("Enter student's mark (0-100): ");  // Prompt user for input
    scanf("%d", &mark);  // Read the input
    
    if (mark < 0 || mark > 100) {  // Validate input range
        printf("Invalid input. Please enter a value between 0 and 100.\\n");
    } else if (mark >= 90) {  // Grade A for marks 90 and above
        printf("Grade: A\n");
    } else if (mark >= 80) {  // Grade B for marks 80-89
        printf("Grade: B\n");
    } else if (mark >= 70) {  // Grade C for marks 70-79
        printf("Grade: C\n");
    } else if (mark >= 60) {  // Grade D for marks 60-69
        printf("Grade: D\n");
    } else {  // Grade F for marks below 60
        printf("Grade: F\n");
    }

    return 0;  // End of the program
}