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  Description:  IOCTL: Generic I/O Control for Character     DOS 3.2 Only
                Devices
 
  Provides a general-purpose mechanism for communication between applica-
  tion programs and character device drivers.
 
  Input                                     Output
  ══════════════════════════════            ══════════════════════════════
  AH=44H                                    If function successful
  AL=0CH                                    Cary flag=clear
  BX=handle                                 and, if called with CL=65H,
  CH=category (major) code:                  6AH, or 6BH
     00=unknown                             DS:DX=segment:offset of para-
     01=COM1, COM2, COM3, or                meter block
         COM4 (3.3)                         If function unsuccessful
     03=CON (keyboard and dis-              Carry flag=set
         play) (3.3)                        AX=error code
     05=LPT1, LPT2, or LPT3
         (3.2)
  CL=function (minor) code:
     45H=Set Iteration Count
          (3.2)
     4AH=Select Code Page
          (3.3)
     4CH=Start Code Page Pre-
          paration (3.3)
     4DH=End Code Page Pre-
          paration (3.3)
     5FH=Set Display Informa-
          tion (4.0)
     65H=Get Iteration Count
          (3.2)
     6AH=Query Selected Code
          Page (3.3)
     6BH=Query Prepare List
          (3.3)
     7FH=Get Display Infor-
          mation (4.0)
  DS:DX=segment:offset of
   parameter block
                                    -♦-