Linked List Example in C++ - a blog of a local hero wannabe

This is an example to using linked list in c++. Lets see below :

# include <iostream.h>
# include <conio.h>

struct TNode{
    char nim[15];
   char nama[30];
   int usia;

   TNode *next;
};

TNode *head;
int opsi = 0;

void init(){
    head = NULL;
}

bool isEmpty(){
    if (head ==NULL) return true;
   else return false;
}

void add_at_front(){
    TNode *baru;
   baru = new TNode;

   cout << "Masukkan NIM    : ";
   cin >> baru-> nim;
   cout << "Masukkan Nama   : ";
   cin >> baru-> nama;
   cout << "Masukkan usia   : ";
   cin >> baru-> usia;
   baru->next = NULL;

   if(isEmpty()==true){
       head=baru;
      head->next = NULL;
   }else {
       baru->next = head;
      head = baru;
   }
   }

void add_at_end(){
    TNode *baru,*bantu;
   baru = new TNode;
   cout << "Masukkan NIM    : ";
   cin >> baru-> nim;
   cout << "Masukkan Nama   : ";
   cin >> baru-> nama;
   cout << "Masukkan usia   : ";
   cin >> baru-> usia;
   baru->next = NULL;

   if(isEmpty()== true){
       head=baru;
      head->next = NULL;
   } else {
       bantu=head;
      while(bantu->next!=NULL){
          bantu=bantu->next;
      }
      bantu->next = baru;
   }
}

void add_at_middle(){
     TNode *baru, *bantu;
     int tmp;
     if(isEmpty()== false){
          cout<<"Setelah data ke berapa data diinsert? : "; cin>>tmp;
          bantu=head;
          baru=new TNode;
          for(int i=1;i<tmp;i++){
          if(bantu->next!=NULL)
               bantu=bantu->next;
          else break;
          }
         cout << "Masukkan NIM    : ";
           cin >> baru-> nim;
         cout << "Masukkan Nama   : ";
           cin >> baru-> nama;
           cout << "Masukkan usia   : ";
         cin >> baru-> usia;
          baru->next=bantu->next;
          bantu->next=baru;
          bantu=baru;
     }
     else cout<<"Data masih kosong, boro-boro bisa masukkan data tengah! ";
}

void del_at_front () {
    TNode *hapus;
   if (isEmpty() == false){
       if(head->next !=NULL){
          hapus = head;
         head = head->next;
         delete hapus;
      } else {
          head = NULL;
      }
   }else {
       cout<<"masih kosong\n";
   }
}

void del_at_end(){
    TNode *hapus, *bantu;
   if (isEmpty()==false){
       if(head->next !=NULL){
          bantu = head;
         while(bantu->next->next!=NULL){
             bantu = bantu->next;
         }
         hapus = bantu->next;
         bantu->next = NULL;
         delete hapus;
      } else {
          head = NULL;
      }

     } else {
          cout<<"masih kosong\n";
     }
}
void del_at_middle(){
        int banyakdata,tmp,poshapus,pdata;
          TNode *hapus, *bantu;

          if(isEmpty()== false){
          cout<<"Data ke berapa data dihapus? : "; cin>>tmp;
          banyakdata=1;
          bantu=head;
          while(bantu->next!=NULL)
          {
                bantu=bantu->next;
                banyakdata++;
          }
                if((tmp<1)||(tmp>banyakdata)){
                cout<<"Posisi di luar jangkauan\n";
           }else {
                   bantu=head;
                    poshapus=1;
                    while(poshapus<(tmp-1))
               {
                    bantu=bantu->next;
                    poshapus++;
                    }
                    hapus=bantu->next;
                    bantu->next=hapus->next;
                    delete hapus;
           }
           }
     else cout<<"Data masih kosong, gak bisa hapus data dari tengah! ";
}

void display_list(){
    TNode *bantu;
   bantu = head;
   if(isEmpty()==true){
       cout<<"masih kosong\n";
   } else {
       cout<<endl<<"--------------------------\n";
      while(bantu!=NULL){
          cout<<"NIM    : " << bantu->nim << " ";
          cout<<"NAMA   : " << bantu->nama<< " ";
          cout<<"USIA   : " << bantu->usia<< " ";
         bantu=bantu->next;
      }
      cout<<endl;
   }
}

void main(){
    int();

   do{
      cout<<endl;
      cout<<"silahkan pilih menu          :"   <<endl;
      cout<<"0. exit program."   <<endl;
      cout<<"1. tambah simpul dari depan."   <<endl;
      cout<<"2. tambah simpul dari belakang."   <<endl;
      cout<<"3. tambah simpul dari tengah."   <<endl;
      cout<<"4. hapus simpul dari depan."   <<endl;
      cout<<"5. hapus simpul dari belakang."   <<endl;
      cout<<"6. hapus simpul dari tengah."   <<endl;
      cout<<"7. tampil data."   <<endl;
      cout<<endl;
      cout<< " >> ";
      cin >> opsi;

      switch(opsi){
          case 1 : add_at_front();break;
         case 2 : add_at_end();break;
         case 3 : add_at_middle();break;
         case 4 : del_at_front();break;
         case 5 : del_at_end();break;
         case 6 : del_at_middle();break;
         case 7 : display_list();break;
      }
   }while (opsi != 0);
}

Enjoy :)