stud.c

#include <stdio.h>
#include <stdint.h>

typedef struct student student;
struct student {
  char name[100];
  char status;
  int id;
};

int main(){
   uint32_t nb_students = 5;
   student class[5] = {
     {"Albert", 'S', 1001},
     {"Maria", 'A', 1002},
     {"John", 'A', 1003},
     {"Harie", 'S', 1004},
     {"Mana", 'F', 1005}
   };

   FILE *fpout = fopen("file.bin", "wb");
   if (fpout==NULL){
     perror("file.bin");
     return 1;
   }

   fwrite("HARI", sizeof(char), 4, fpout);
   fwrite(&nb_students, sizeof(uint32_t), 1, fpout);
   fwrite(class, sizeof(struct student), nb_students, fpout);
   fclose(fpout);

   FILE *fpin = fopen("file.bin", "rb");
   if (fpin==NULL){
     perror("file.bin");
     return 1;
   }
   char HARITag[4] = {0};
   fread(HARITag, sizeof(char), 4, fpin);
   if (strncmp(HARITag, "HARI", 4)){
     printf("%s: unrecognized file format\n", "file.bin");
     return 1;
   }

   /* overwrites nb_students value with what is read */
   fread(&nb_students, sizeof(uint32_t), 1, fpin);
   /* overwrites class values with what is read */
   fread(class, sizeof(struct student), nb_students, fpin);
   fclose(fpin);

   for (int i = 0; i < nb_students; i++)
     printf("%s %c %d\n", class[i].name, class[i].status, class[i].id);



   return 0;
}