#include <stdio.h>

char user_name[20] = "                   ";
char password[20] = "                   ";
char users[][2][20] =
{ { "root", "98765" },
  { "moi", "allo" },
  { "abc", "motdepasse" },
  { "", "" }
};

int check_name()
{
  int i;
  printf("Name: "); gets(user_name);
  printf("Pass: "); gets(password);

  for(i=0; users[i][0][0] != 0; i++)
  {
    if(strcmp(user_name, users[i][0]) == 0 &&
       strcmp(password,  users[i][1]) == 0)
       return 1;
  }
  return 0;
}

void logon()
{
  printf("Welcome to system...\n");
  exit(1);
}

void reject()
{
  printf("Connection refused!\n");
  exit(0);
}

main()
{
  unsigned int i;
  for(i=(unsigned)-3; i && !check_name(); i++);
  if(i>=(unsigned)-3)
    logon();
  else
    reject();
}