You had a bunch of errors in there, 19 to be exact from the start. So I cleaned up the code a bit and fixed the errors, as well as added some much needed formatting ![Wink](https://cboard.cprogramming.com/images/smilies/wink.png)
Look at what you had before and what I've done and see if you can find the differences and why I put them there. Take note that I didn't check to see if the program works as planned, that's your job. I just made sure that it compiles.
Code:
# include <stdio.h>
int main(void){
/* Variable declarations: */
int idno, test1, test2, final_test,total_number_of_A = 0,total_number_of_B = 0,
total_number_of_C = 0, total_number_of_D = 0, total_number_of_F = 0;
double semester_average = 0.0, class_average = 0.0;
int number_of_students = 0;
/* Function body: */
printf ("***> Enter student idno:");
scanf ("%d", & idno);
printf ("***> Enter test1:");
scanf ("%d", & test1);
printf ("***> Enter test2:");
scanf ("%d", & test2);
printf ("***> Enter final_test:");
scanf ("%d", & final_test);
while (idno != 0) {
semester_average=0.20*test1+0.30*test2+0.50*final_test;
printf ("The semester average is %lf\n", semester_average);
if (semester_average >= 90 && semester_average <= 100){
printf ("The letter grade is A\n");
total_number_of_A = total_number_of_A+1;
}
if (semester_average >= 80 && semester_average <= 89){
printf ("The letter grade is B\n");
total_number_of_B = total_number_of_B+1;
}
if (semester_average >= 70 && semester_average<= 79){
printf ("The letter grade is C\n");
total_number_of_C = total_number_of_C+1;
}
if (semester_average >= 60 && semester_average <= 69){
printf ("The letter grade is D\n");
total_number_of_D = total_number_of_D+1;
}
if (semester_average >= 0 && semester_average <= 59){
printf ("The letter grade is F\n");
total_number_of_F = total_number_of_F+1;
}/* end if */
printf ("***> Enter student idno:");
scanf ("%d", & idno);
if(idno == 0){ break; }
printf ("***> Enter test1:");
scanf ("%d", & test1);
printf ("***> Enter test2:");
scanf ("%d", & test2);
printf ("***> Enter final_test:");
scanf ("%d", & final_test);
} /* end while */
/*Calculate Class Average*/
class_average = ((4 * total_number_of_A) + (3 * total_number_of_B) +
(2 * total_number_of_C) + (1 * total_number_of_D))/
number_of_students;
printf("Grade distribution:");
total_number_of_A = total_number_of_A + 1; printf("%d", total_number_of_A);
total_number_of_B = total_number_of_B + 1; printf("%d", total_number_of_B);
total_number_of_C = total_number_of_C + 1; printf("%d", total_number_of_C);
total_number_of_D = total_number_of_D + 1; printf("%d", total_number_of_D);
total_number_of_F = total_number_of_F + 1; printf("%d", total_number_of_F);
printf("Class average: %lf", class_average);
return 0;
} /* end function main */