[TIP] DO NOT USE fflush function

#include <stdio.h>

int main(void)
{
	int number;
	char grade;

	printf("Type in ClassNumber : ");
	scanf_s("%d", &number);
	
    /* If want to remove data from Buffer */
	fflush(stdin); <- DO NOT USE
    getchar();	<- RECOMMEND

	//printf("Type in Grade: ");
	scanf_s("%c", &grade);

	printf("Number: %d, Grade: %c", number, grade);

	return 0;
}