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  New Features in DOS Version 4

  Interrupt 21H Functions in DOS Version 4
    Function 33H (decimal 51): Get/Set System Value
    Function 44H (decimal 68): IOCTL--I/O Control for Devices
    Function 65H (decimal 101): Get Extended Country Information
    Function 6CH (decimal 108): Extended Open/Create

  Interrupts 25H and 26H

  The DOS Version 4 Disk Boot Sector
    The Extended BIOS Parameter Block
    The Volume Serial Number

  A Sample Routine

  DOS Version 4 in Perspective