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  Function 12H (decimal 18) finds the next of a series of files, following
  the set-up preparation performed by function 11H. As with function 11H,
  you must call function 12H with the address of an FCB in DS:DX. For
  function 12H, the FCB should be the same as the one you used for a
  successful call to function 11H.

  DOS reports a successful match by returning AL = 00H; if no match exists,
  DOS returns AL = FFH. This lets you combine functions 11H and 12H to
  perform a complete directory search by using the following logic:

  initialize FCB
  call function 11H
  WHILE AL = 0
          use current contents of DTA
          call function 12H