Function 14h (20)        Sequential Read, Using FCBs

    Reads the next sequential record from a file, then increments the
    FCB's current block and current record fields.

       On entry:      AH         14h
                      DS:DX      Pointer to an opened FCB

       Returns:       AL         00h      If read was successful
                                 01h      If EOF encountered and no data read
                                 02h      If DTA too small (segment wrap)
                                 03h      If EOF encountered and partial
                                          record read

       Network:       Requires Read access rights

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       Notes:         The sequential record number is taken from the
                      values in the current block (offset 0Ch) and the
                      current record (offset 20h) fields of the FCB. These
                      fields are automatically updated after the read
                      operation. The number of bytes to read is taken from
                      the record size field at offset 0Eh of the FCB.

                      The data is read in at the current Disk Transfer
                      Address (DTA). Use Function 1Ah to set the DTA. If
                      the transfer of data would cause segment wraparound,
                      an error 2 is generated.

                      If an EOF is encountered before a full record has
                      been read, the remainder of the record is padded to
                      the requested size with zeros.