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  Function 5AH (decimal 90) was introduced in DOS version 3.0. It creates a
  file for temporary use. It generates a unique filename for the file by
  building the name from the current time of day. You provide two
  parameters: the file attribute, placed in the CX register, and the
  pathname of the directory where the file will be created. The pathname
  must be an ASCIIZ string and is pointed to by the register pair DS:DX.

  The pathname string must be ready to have the filename of the created file
  appended to it: The string must end with a backslash character and be
  followed by 13 bytes to allow enough room for DOS to add a filename to the
  string. If you don't want to specify a particular path, you can give DOS a
  null string, which tells it to use the current directory of the current
  drive.

  If function 5AH successfully creates a file, it clears the carry flag and
  returns the name of the file appended to the pathname you specified in
  DS:DX. If the function fails, it sets the carry flag and returns an error
  code in AX: 03H (path not found), 04H (no more handles), or 05H (access
  denied).

  This function is called "create temporary file" only to suggest its
  intended purpose. Actually, there is nothing temporary about the file that
  is created because DOS does not automatically delete it; your programs
  must look after that chore.