qa.hlp (Table of Contents; Topic list)
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Int 21H Function 01H
   Summary  Notes  Back
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▀ If the standard input is not redirected and the character read is a
  CTRL+C, an Int 23H is executed. If the standard input is redirected, a
  CTRL+C is detected at the console, and BREAK is ON, an Int 23H is
  executed.
 
▀ To read extended ASCII codes (such as the special function keys F1 to
  F10) on the IBM PC and compatibles, you must call this function twice.
  The first call returns the value 00H to signal the presence of an ex-
  tended code.
 
▀ See also Int 21H Functions 06H, 07H, and 08H, which provide character
  input with various combinations of echo and/or CTRL+C sensing.
 
▀ You can also read the keyboard by issuing a read (Int 21H Function 3FH)
  using the predefined handle for the standard input (0000H), if input
  has not been redirected, or using a handle obtained by opening the
  logical device CON.
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