由单道批处理系统转化为多道批处理系统所存在问题的代码理解

// Demo.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include "Demo.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

/////////////////////////////////////////////////////////////////////////////
// The one and only application object
 CWinApp theApp;
 using namespace std;
 static void sub(void *c);

int _tmain(int argc, TCHAR* argv[], TCHAR* envp[])
{
    int nRetCode = 0;
    /*
	//initialize MFC and print and error on failure
	if (!AfxWinInit(::GetModuleHandle(NULL), NULL, ::GetCommandLine(), 0))
	{
		//TODO: change error code to suit your needs
		cerr<< _T("Fatal Error: MFC initialization failed") << endl;
		nRetCode=1;
	}
	else
	{
		//TODO: code your application's behavior here.
		CString strHello;
		strHello.LoadString(IDS_HELLO);
		cout << (LPCTSTR)strHello << endl;
	}
*/
       char val='a';
	   char cb='A';
	   unsigned long v;
	   HANDLE ha[2];
	   ha[0]=::CreateThread(NULL,0,(LPTHREAD_START_ROUTINE)sub,&val,0,&v);
	   ha[1]=::CreateThread(NULL,0,(LPTHREAD_START_ROUTINE)sub,&cb,0,&v);
	   ::WaitForMultipleObjects(1,ha,true,INFINITE);
       return nRetCode;
}

 
 static void sub(void *c)
 {
  char *p=(char *)c;
  char b;
  for(int i=0;i<26;i++)
  {
      //cout<<*p<