Output:
Exer6

#include

#include
float grade, average, items, sum;

void main(){

clrscr();

average=0;sum=0;do{

printf("Enter grade (-1 to exit): ");

scanf("%f", &grade);

if((grade!=-1)&&(grade<=100)){items++;sum=sum+grade;}}

while(grade!=-1);
average=sum/items;printf("Class Average: %.2f\n", average);
if((average>=95)&&(average<=100)){

printf("Rating: A");}

else if((average>=90)&&(average<=94)){printf("Rating: B");}

else if((average>=85)&&(average<=89)){printf("Rating: C");}

else if((average>=80)&&(average<=84)){printf("Rating: D");}

else if((average>=75)&&(average<=79)){printf("Rating: E");}

else if(average<=74){printf("Rating: FAILED");} getch();

}