beneath-apple-dos/CHANGES-2nd-printing.txt

SECOND PRINTING CORRECTIONS


3-3

Data bits are recorded on the
diskette in precise intervals.  For
the purposes of this discussion, the
demarcation of these intervals will
be depicted by a clock bit.  Using
this representation, data written to
and read back from the diskette takes
the form shown in Figure 3.2.  The
data pattern shown represents a
binary value of 101.


3-10

at least as long as a typical Gap 3
(in practice its length is usually
more than 400 sync bytes, enabling it
to serve as a Gap 3 type for Address
Field number 0 (See Figure 3.7 for
clarity).


3-17

page.*

diagrammed in Figure 3.21.*

*Figures 3.20 and 3.21 present the
nibblizing process used by the "6 and
2" encoding technique.  However, the
concept is the same for the "5 and 3"
technique.


4-17

occurred. Either a bad checksum was detected on the data in a

program given there will read any
track/sector on an unprotected
diskette into memory, allowing the
user to examine it or modify the data
and then, optionally, rewrite it to a
diskette.  Using such a program is
very important when learning about
diskette formats and when fixing
clobbered data.


5-2

The file manager, occupying about
2.8K, is a collection of

5-5     (note correction to correction - first $3F2 is ok)

      change $3F2 to handle your own RESETs, EOR (exclusive
      OR) the new value at $3F3 with a $A5 and store the
      result in the power-up byte.


6-5

NOTE: RWTS uses zero-page location
$48, which is also used by the
APPLE
monitor to hold the P-register value.
Location $48 should be set to zero
after each call to RWTS.


6-11

             04/05 - Byte offset of current file position*

*The current file position is updated
to point to the byte following the
data read or written.


8-5

9E51-9E7F An image of the DOS page 3 jump vector which the
          above routine copies to $3D0-$3FF. See Chapter 5 for
          a description of its contents.


8-36

B9A0-B9FF SEEKABS routine.
          Move disk arm to desired track.
          Calls arm move delay subroutine ($BA00).


8-37

BA00-BA10 Arm move delay subroutine.


A-3

A diskette containing these five
programs is available at a reasonable
cost directly from Quality Software,
6660 Reseda Blvd., Reseda, CA. or
telephone (213) 344-6599.

A-12

at location $03 (the volume number
should match the volume number of the
other tracks), and then begin
execution at $800.  INIT will return
to the monitor upon completion.  If
the track can not be formatted for
some reason (eg.  physical damage or
problems with the disk drive itself)
a return code is printed.  For
example:


A-20

800G                    (Run the COPY program)