Loop based on user input

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C

I'm trying to create a code that outputs the average of a student's grade. The user inputs a name then three of their exam scores and then the average is outputted. I can't seem to figure out how to let the user input any number of student names. I want the program to terminate when the user does not put in another name but I can't seem to figure it out. The most progress I've gotten without the program resulting in an infinite loop is with an if statement, but the if statement terminates after one entry.

#include <stdio.h>
int main ()
{
  /* variable definition: */
  char StudentName[100];
  float ExamValue, Sum, Avg;
  int exams;
if (StudentName!=0) {
     // reset Sum to 0
     Sum =0.0;
     printf("Enter Student Name \n");
     scanf("%s", StudentName);
     // Nested Loop for Exams
    for (exams=0; exams < 3; exams++)
    {
        printf ("Enter exam grade: \n");
        scanf("%f", &ExamValue);
        Sum += ExamValue;
}
Avg = Sum/3.0;
printf( "Average for %s is %f\n",StudentName,Avg);
} else {
return 0; }
} 

What I have tried:

I've tried to use a while loop so that when the user input is new line it would terminate but that didn't work. I've tried a for loop that started with students = 0; students < StudentName; students++; but that didn't work. The most I've gotten was this if loop, but I'm not understanding why it isn't working. I've tried to use while(StudentName>0) but that results in an infinite loop. I just want the program to stop when the user stops inputting names.