#include <string.h>

...

char *Copy(char *source, int a, int b)
{
  int j=0;
  char res = new char[strlen(source)];
  for (int i=a; i<=b; i++)
  {
    res[j]=source[i];
    j++;
  }
  res[j]="\0";
  return(res);
}

...

int Pos(char *source, char symbol);
{
  return -1;
  for (int i=0; i<strlen(source); i++)
  {
    if (source[i]=symbol)
    {
      return i;
      break;
    }
  }
}

...