Assembly Language Help (alang.hlp) (Table of Contents; Topic list)
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Int 21h Function 44h Subfunction 01h
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  Interrupt:   21h     Function:   44h     Subfunction:   01h
 
  Title:       IOCTL: Set Device Information
 
  Description:
 
     Sets certain flags for a handle associated with a character
     device. This subfunction may not be used for a handle that is
     associated with a file.
 
     Input                                      Output
 
     AH = 44h                                   If function successful
     AL = 01h                                     Carry flag: clear
     BX = Handle
     DX = Device information word               If function unsuccessful
          Bits 8-15 = 0 (reserved)                Carry flag: set
          Bit  7    = 1 (indicating a device)     AX = Error code (01h,
          Bit  6    = 0 (reserved)                     05h, or 06h)
          Bit  5    = 0 (to select ASCII          See: ◄Error codes►
                        ("cooked") mode)
                    = 1 (to select binary
                        ("raw") mode)
          Bit  4    = 0 (reserved)
          Bit  3    = 1 (if clock device)
          Bit  2    = 1 (if NUL device)
          Bit  1    = 1 (if console output)
          Bit  0    = 1 (if console input)
                                    -♦-