INT 21 - MS-DOS 7.0+ - GENERIC IOCTL - GET FIRST CLUSTER
	AX = 440Dh
	CX = 0871h (category code 08h/48h, minor code 71h)
	BX = filename character set (see #01578)
	DS:DX -> ASCIZ pathname for file or directory
Return: CF set on error
	AX = error code (01h,02h,etc.)
	CF clear if successful
	DX:AX = first cluster number
Note:	this function finds any file or directory regardless of attributes,
	except that it will not find volume labels
(Table 01578)
Values for character set:
 00h	Windows ANSI
 01h	current OEM character set
 02h	Unicode
Values for block device IOCTL category code:
 08h	disk drive
 48h	FAT32 disk drive

#define Not_VxD

#include <stdio.h>
#include <windows.h>
#include "VWin32.h"

void main()
{
  char szPathName[] = "c:\\command.com";
  HANDLE hVWin32;
  DIOC_REGISTERS regs;
  DWORD cb;

  hVWin32 = CreateFile("\\\\.\\VWIN32", 0, 0, NULL, 0, 0, NULL);

// Lock logical volume
  regs.reg_EAX = 0x440D;
  regs.reg_EBX = 0x103;  // Level 1, drive C:
  regs.reg_ECX = 0x84A;          
  regs.reg_EDX = 7;
  DeviceIoControl(hVWin32, VWIN32_DIOC_DOS_IOCTL,
                           ®s, sizeof(regs),
                           ®s, sizeof(regs), &cb, NULL);
  if (regs.reg_Flags & 1)
     printf("Error: Couldn't lock volume!\n");

// Get 1'st cluster
  
  regs.reg_EAX = 0x440D;
  regs.reg_EBX = 0;
  regs.reg_ECX = 0x0871;          
  regs.reg_EDX = (DWORD) &szPathName;
  DeviceIoControl(hVWin32, VWIN32_DIOC_DOS_IOCTL,
                           ®s, sizeof(regs),
                           ®s, sizeof(regs), &cb, NULL);
  if (regs.reg_Flags & 1)
     printf("Error: %d\n", regs.reg_EAX);
  else
     printf("Filename: %s\n1'st cluster = 0x%X\n",
             szPathName, MAKELONG(regs.reg_EAX, regs.reg_EDX));

// Unlock logical volume
  regs.reg_EAX = 0x440D;
  regs.reg_EBX = 3;
  regs.reg_ECX = 0x86A;
  DeviceIoControl(hVWin32, VWIN32_DIOC_DOS_IOCTL,
                           ®s, sizeof(regs),
                           ®s, sizeof(regs), &cb, NULL);
  CloseHandle(hVWin32);
}