BOOL CreateDirectory(
LPCTSTR lpPathName, // directory name
LPSECURITY_ATTRIBUTES lpSecurityAttributes // SD
);

void main()
{
if (CreateDirectory(”c:\\new”,NULL))
 printf("Done!\n");
else
 printf("Error\n");
}

if( /* условие */)
  return 0; // или return 1

if( /* условие */)
  exit(0);

# include <iostream>
# include <stdlib.h>
int main() {
    int n, a0, a1, a2, a3;
    char a01, a11, a12;
    printf("Enter n, please:");
    scanf("%d", &n);
    a0=(n/1000);
    a1=(n/100)-a0*10;
    a2=(n/10)-(a0*100+a1*10);  
    a3=n-(a0*1000+a1*100+a2*10);
    
    if (n<10) {
              printf("Error: n have only one digital");
              exit();
    }
    else if (n>9999) {
         printf("Error: n>9999");
    }
    else {}
    
    if (a0==0 && a3!=0) {
              a0=n+1;
       }
    else if (a1==0 && a3!=0) {
              a1=n+2;              
       }
    else if (a2==0 && a3!=0) {
              a2=n+3;
       }
    else {}
    
    if (a0==a1 || a0==a2 || a0==a3 || a1==a2 || a1==a3 || a2==a3) {
       printf("YES!");
       }
    else {
       printf("NO!");
    }
}

#include <iostream>
#include <windows.h>
using namespace std;


void main()
{
if (CreateDirectory("c:\\new",NULL))
 cout << "Done!\n";
else
 cout <<"Error\n";
}

error C2664: 'CreateDirectoryW' : cannot convert parameter 1 from 'const char [7]' to 'LPCWSTR'

if (n<10) {
              printf("Error: n have only one digital");
              exit(1);
    }