이 코드 돌려서 입력 계속하면 입력된게 계속 쌓여야 되는데

입력 할때마다 마지막 한개만 남네..

문제가 뭔지 -_-...

짤은 조공..

#include <stdio.h>

#include <stdlib.h>

typedef struct STUDENT
{
 char name[50],adress[100];
 int PN[10],STN[10];
 float grade[10];
 struct STUDENT *prev;
 struct STUDENT *next;
}st;
st  *head=NULL;  //node pointer
st *tail=NULL;
//initialization
void initi()
{
 head=(st*)malloc(sizeof(st));
 tail=(st*)malloc(sizeof(st));
 head->next=tail;
 head->prev=head;
 tail->prev=head;
 tail->next=tail;
}

void insertnode(st *insert)
{
 st *newnode;
 newnode=(st*)malloc(sizeof(st));
 newnode = insert;
 tail->prev->next=newnode;
 newnode->prev=tail->prev;
 tail->prev=newnode;
 newnode->next=tail;
}

void show_print()
{
 st *tmp;
 tmp=head->next;
 while(tmp != tail)
 {
  printf("-----------------------------------------------------------------\\n");
  printf("    Name    | Student ID |   Adress   | Phone Number | Grade |\\n");
     printf("-----------------------------------------------------------------\\n");
 {
   printf("%12s|", tmp->name);
   printf("%12d|", *tmp->STN);
   printf("%12s|", tmp->adress);
   printf("%12d|", *tmp->PN);
   printf("%12f|\\n", *tmp->grade);
  }
 printf("-----------------------------------------------------------------\\n");
 tmp=tmp->next;
 }
}
struct MAJOR
{
 char name[500];
 int PN[10];
};
struct PROFESSOR
{
 char name[500],adress[500];
 int PN[10],EN[10];
};
int main(void)
{

// st *std;
 st *copy;
 int mode; 
 int i=1, m;

 //std = (struct STUDENT*)malloc(sizeof(std)*i);

 copy = (struct STUDENT*)malloc(sizeof(st));
 initi();
 for(;;){
 printf("#########################################\\n");
 printf("#\\tGrade management programs\\t#\\n");
 printf("# 1. Registration of student\\t\\t#\\n");
 printf("# 2. List of registered student\\t\\t#\\n");
 printf("# 3. Registration of professor\\t\\t#\\n");
 printf("# 4. List of registered professor\\t#\\n");
 printf("# 5. Registration of major\\t\\t#\\n");
 printf("# 6. List of registered major\\t\\t#\\n");
 printf("# 7. EXIT\\t\\t\\t\\t#\\n");
 printf("#########################################\\n");
 printf("Select mode : ");
 scanf("%d", &mode);

 if(mode==1){
    
  
  printf("Enter Student name : ");
  scanf("%s", copy->name);
  printf("Enter Student ID : ");
  scanf("%d", copy->STN);
  printf("Enter Adress : ");
  scanf("%s", copy->adress);
  printf("Enter Phone number : ");
  scanf("%d", copy->PN);
  printf("Enter Grade : ");
  scanf("%f", copy->grade);
  insertnode(copy);
  
  printf(" registration of %d student\\n", i);
  i++;
 }
 else if(mode==2){
  show_print();

 }
 else if(mode==7){
  printf("Bye\\n");
  break;
 }
 }
 free(copy);
 return 0;
}