C Program to read records from a file and calculate grade of each student and display it

C Program to read records from a file and calculate grade of each student and display it 

grade= A if marks>=80

= B if marks>=60 and < 80


= C if marks<60

#include<stdio.h>

#include<stdlib.h>

int main(void)

{

 struct record

 {

  char name[20];

  int roll;

  int marks;

 }student;

 FILE *fp;

 fp = fopen("stu","rb");/*opened in read mode */

 if(fp==NULL)

 {

  printf("Error in opening file\n");

  exit(1);

 }

 printf("\nNAME\t\tMARKS\t\tGRADE\n\n");

 while(fread(&student,sizeof(student),1,fp)==1)

 {

  printf("%s\t\t",student.name);

  printf("%4d\t\t",student.marks);

  if(student.marks>=80)

   printf("A\n");

  else if(student.marks>=60)

   printf("B\n");

  else

   printf("C\n");

 }

 fclose(fp);

 return 0;

}