#define RECORD_SIZE 47   /* Maximum number of characters in 
                                   the record including 1 
                                   for the NUL character */
     char buffer[RECORD_SIZE];
     int record_number;

     /* Write a record */     
     record_number = 12;
     sprintf(buffer, "%s %d ",a,xx...);
     fseek(file,(long) RECORD_SIZE * record_number, 0);
     fwrite(buffer,RECORD_SIZE,1,file);
     
     /* Read a record */     
     record_number = 12;
     fseek(file,(long) RECORD_SIZE * record_number, 0);
     fread(buffer,RECORD_SIZE,1,file);
     sscanf(buffer, "%s %d ",&a,&xx...);