caesar chiper c++

#include <cstdlib>
#include <iostream>
#include <string.h>
#define maks 500
using namespace std;

//int main(int argc, char *argv[])
class Enskripsi
{
      public:
             Enskripsi();
      void enskripsi();
      void deskripsi();
      void output();
      private:
              char chiper[maks];
              int key;
              char plain[maks];
              };
              Enskripsi::Enskripsi(){
              cout<<"masukkan kata:";
              cin.getline(chiper,sizeof(chiper));
              cout<<"masukkan key:";
              cin>>key;
              cout<<endl;
              }
             
      void Enskripsi::enskripsi(){
           for(int i=0;i<strlen(chiper);i+=1){
                   cout<<chiper[i]<<" ("<<int(chiper[i])<<") ";
                   chiper[i]=(chiper[i]+key)%128;
                   }}
                  
           void Enskripsi::deskripsi(){
                for(int i=0;i<strlen(chiper);i+=1){
                plain[i]=(chiper[i]-key)%128;
                chiper[i]=plain[i];
                }}
               
           void Enskripsi::output(){
           for(int i=0;i<strlen(chiper);i+=1){
                   cout<<chiper[i];
                   }}
                   int main(int argc, char *argv[])
                   {
                       Enskripsi Deskripsi;
                       Deskripsi.enskripsi();
                       cout<<"\n\nsetelah dienskripsi:";
                       Deskripsi.output();
                       Deskripsi.deskripsi();
                       cout<<"\n\nkembali dideskripsi:";
                       Deskripsi.output();
                      
                   cout<<endl<<endl;
                  
    system("PAUSE");
    return EXIT_SUCCESS;
}

program bilangan. primaa c++

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

using namespace std;

//nt main(int argc, char *argv[])
int main()
{
     int x,a,b;
     char i;
     {
          b=1;
         // i1:clrscr();
         cout<<"PROGRAM UNTUK MEMERIKSA BILANGAN PRIMA"<<endl<<endl;
          cout<<"Masukkan Bilangan Untuk di Cek: ";
          cin>>x;
          //cout<<endl;
          for(a=2;a<=x-1;a++)
          {
          if(x%a==0)
          {
                        b=0;
                        break;
                        }
                        }
                        if (b==1)
                        {
                        cout<<x<<"merupakan bilangan prima";
                         }
                         else
                          {
                           cout<<x<<"bukan bilangan prima";
                           }
                            if(b==0)
                            cout<<endl;
                            cout<<endl;
                            cout<<endl;
                            cout<<"ulangi (y/n) ?";
                            cin>>i;
                            if(i=='y'){}
                           // goto i1,
                            else
                            cout<<"terima kasih";
                           
                            }
    system("PAUSE");
    return EXIT_SUCCESS;
}