Int 62 Fn 0A  - Cswitch - Test Message Queue                               [T]

   AH = 0Ah
   DX = queue number (0-63)

Return: AX = result/message size
       0000h nothing on queue
       FFFFh bad queue number
       else  number of bytes in first message in queue

See Also: AH=0Bh"Cswitch",AH=0Ch"Cswitch"