C Code; nested do while loops with inputs - c

Question

So I got some awesome assistance the other day with a C code problem, hoping this one can generate similar responses. First task is to write a code to accept an unknown number of names. Second is to allow input of an unknown number of values (grades) for each name, and each set of values is averaged and printed with the name. There is a similar thread i read and found some inspiration, but it still isn't compiling right.
I am not married to any particular part of this code, but I was trying to keep it simple with nested Do...while loops. I have tried several different approaches, all fall short of elegantly expressing the unknown number of values assigned to an unknown number of people.
My hope is that the user will be prompted to enter a name, then as long as that value isnt nulled out, the user is immediately prompted to enter grade values that are tabulated in a running total. When the value of grade goes null, the loop quits and the sum total is averaged. The name and average are printed together until the name value is null and then the sub quits. Greatly appreciate any input from the community.
#include <stdio.h>
#include <math.h>
int main(){
char b, stu_name;
float grade, sum, avg;
int i,counter;
do{
printf("Enter a student's name? \n");
scanf("%s", &stu_name);
do{
printf("How many grades are to be entered for this student? \n");
scanf("%d", &i);
for (counter = 0; counter < i; counter++) {
printf("Enter %s's grade, hit enter and enter another \n");
scanf("%f", &grade);
sum = sum + grade;
} while (grade != '\0');
avg = sum/i;
printf("GPA for %s is %f\n", stu_name,avg);
printf("Press any key to enter another student");
scanf("%c",b);
}while (b != '\0');
return(0);}

Answer 1

You're missing the ending brace on the for loop, as Helio Santos pointed out.
You're also having various syntax-type problems:
For the "Enter grade" prompt, you need a %c not a %s as you only
defined stu_name as a char not a char[]
The end of the interior Do/While loop should be checking against i, not grade
That check should also be against a value that scanf could return in your setup; the %d will force trying to get a numeric value

Answer 2

Bam! Compilation success. Thanks much, I appreciate the help. Doesn't look like i can test it fully (notice the whacked out GPA down below) because i don't know how use this online compiler to add a grade more than once (in the loop). If anyone knows whats going on with the GPA stdout i am all ears, going to the next step of the assignment with this code.
*edit after some more comments. Currently rockin the below code. It works...but only 3-4 times for some reason.
#include <stdio.h>
#include <math.h>
int main(){
char b;
char stu_name[75];
float grade, sum, avg;
int i,counter;
do{
printf("Enter a student's name? \n");
scanf("%s", stu_name);
b = '\0'
i = 0;
sum = 0;
printf("How many grades are to be entered for this student? \n");
scanf("%d", &i);
for (counter = 0; counter < i; counter++) {
printf("Enter %s's grade, hit enter and input another \n",stu_name);
scanf("%f", &grade);
sum = sum + grade;}
avg = sum/i;
printf("GPA for %s is %f\n", stu_name,avg);
stu_name[0]= '\0';
printf("Type q or Q to quit or enter to input another student \n");
scanf(" %c", &b);
} while (b != 'q' && b!='Q');
return(0);}