qa.hlp (Table of Contents; Topic list)
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Int 21H Function 40H
   Summary  Notes  Example  Back
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▀ If the carry flag is returned clear but AX < CX, then a partial record
  was written or there is an error. This can be caused by a CTRL+Z (1AH)
  embedded in the data if the destination is a character device in cooked
  mode or by a disk-full condition if the destination is a file.
 
▀ If the function is called with CX = 0, the file is truncated or extended
  to the current file pointer position.
 
▀ [3.0+] If the program is running on a network, the user must have Write
  access rights to the directory and file.
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