Apple II
Technical Notes
_____________________________________________________________________________
                                                  Developer Technical Support

ProDOS 8
#23:    ProDOS 8 Changes and Minutia

Revised by:    Matt Deatherage                                 September 1990
Written by:    Matt Deatherage                                      July 1989

This Technical Note documents the change history of ProDOS 8 through V1.9, and 
it supersedes the information on this topic in the ProDOS 8 Technical 
Reference Manual and the ProDOS 8 Update.
Changes since March 1990:  Updated to include ProDOS 8 version 1.9 and its 
known bugs.
_____________________________________________________________________________


Changes?  You're kidding.

No.  One of the side effects of evolving technology is that eventually little 
things (like the disk operating system) have to change to support the new 
technologies.  Every time Apple changes ProDOS 8, the manuals can't be 
reprinted.  For one thing, it takes a long time to turn out a manual, by which 
time there's often a new version done which the new manual doesn't cover.  For 
another thing, programmers and developers don't tend to purchase revised 
manuals (our informal research shows that more people have up-to-date Apple 
/// RPS documentation than have up-to-date Apple IIc documentation--and this 
was done before the Apple IIc Plus was released...).

So this Note explains what has changed between ProDOS 8 V1.0 and the current 
release, V1.9, which began shipping with System Software 3.2.  Table 1 shows 
what versions of ProDOS 8 existing documentation covers.

                                                       Version
    Document                                           Number
    ___________________________________________________________
    ProDOS 8 Technical Reference Manual                1.1.1
    ProDOS 8 Update                                    1.4
    AppleShare Programmer's Guide to the Apple IIgs    1.5
    ___________________________________________________________

    Table 1-ProDOS 8 Documentation

ProDOS 1.0

This was the first release of ProDOS, which was so unique it didn't even have 
to be called ProDOS 8 to distinguish it from ProDOS 16.  If you have 
documentation that predates ProDOS 1.0, you should seek professional help from 
APDA at the address listed in Technical Note #0.

ProDOS 1.0.1

  o  Fixed a bug in the STATUS call which affected testing for the 
     write-protected condition.

ProDOS 1.0.2

  o  Changed instructions used in interrupt entry routines on the 
     global page so the accumulator would not be destroyed.
  o  Fixed a bug in the Disk II core routines so the motor would shut 
     off after recalibration on an error.

ProDOS 1.1

  o  Changed the internal MLI layout for future expansibility and 
     maintenance.
  o  Modified machine ID routines to identify IIc and enhanced IIe 
     ROMs.
  o  Removed code that allowed ProDOS to boot on 48K machines.
  o  Removed the check for the ProDOS version number from the OPEN 
     routine.
  o  Incremented KVERSION (the ProDOS Kernel version) on the global 
     page.
  o  Modified the loader routines to reflect the presence of any 80-
     column card following the established protocol (see ProDOS 8 
     Technical Note #15, How ProDOS 8 Treats Slot 3).  Also, at this 
     time, added code to allow slot 3 to be enabled on a IIe if an 80-
     column card following the protocol was found.
  o  Added code to turn off all disk motor phases prior to seeking a 
     track in the Disk II driver.
  o  Fixed a bug to prevent accesses to /RAM after it had been removed 
     from the device list.
  o  Reduced the size of the /RAM device by one block to protect 
     interrupt vectors in the auxiliary language card.  The correct 
     vectors are installed at boot time.

ProDOS 1.1.1

  o  Fixed a Disk II driver bug for mapping into drive 1.
  o  Modified machine ID routines to give precedence to identifiable 
     80-column cards in slot 3.

ProDOS 8 1.2

  o  Changed the name from ProDOS to ProDOS 8 to avoid confusion with 
     ProDOS 16, which, again, this Note does not discuss.
  o  Introduced the clock driver for the Apple IIgs.  The machine 
     identification code was changed to indicate the presence of the 
     clock on the IIgs.
  o  Added preliminary network support by adding the network call and 
     preliminary network driver space.
  o  Fixed a bug in returning errors from calls to the RAM disk.  
     Changed the RAM disk driver to return values of zero on reads and 
     ignore writes to blocks zero, one, four, five, six, and seven, 
     which are not accessible as storage in the driver's design.
  o  Added a new system error ($C) for errors when deallocating blocks 
     from a tree file.
  o  Fixed a bug in zeroing a Volume Control Block (VCB) when trying to 
     reallocate a previously used VCB.
  o  Modified the ProDOS 8 loader code to automatically install up to 
     four drives in slot 5 if a SmartPort device is found.  Removed the 
     code to always leave interrupts disabled, which leaves the state 
     of the interrupt flag at boot time unchanged while ProDOS 8 loads.
  o  Changed the MLI entry to disable interrupts until after the 
     MLIACTV flag is set and other ProDOS parameters are initialized.
  o  Modified the QUIT code to allow the Delete key to function the 
     same as the left arrow key.  Also fixed a bug so screen holes 
     would not be trashed in 80-column mode.  Crunched code to allow 
     soft switch accesses to force 40-column text mode.  Fixed a bug so 
     the dispatcher would not trash the screen when executed with a NIL 
     prefix.
  o  Modified the ONLINE call so that it could be made to a device that 
     had just been removed from the device list by the standard 
     protocol.  Previous to this change, a VCB for the removed device 
     was left, reducing the number of on-line volumes by one for each 
     such device.  From this point on, removing a device should be 
     followed by an ONLINE call to the device just removed.  The call 
     returns error $28 (No Device Connected), but deallocates the VCB.
  o  Added a spurious interrupt handler to allow up to 255 unclaimed 
     interrupts before system death.
  o  Removed the code which invoked low-resolution graphics on system 
     death--it had not worked well and the space was needed.  The system 
     had previously had the ability to display "INSERT SYSTEM DISK AND 
     RESTART" without also displaying "-ERR xx", which was removed at 
     this point for space reasons since the system wasn't using it (and 
     hopefully you weren't, either, since it wasn't documented).
  o  Changed MLIACTV to use an ASL instead of an LSR to turn "off" the 
     flag.
  o  Changed the OPEN call to correctly return error $4B (Unsupported 
     Storage Type) instead of error $4A (incompatible file format for 
     this version) when attempting to open a file with an unrecognized 
     storage type.
  o  Fixed an obscure bug involving READ in Newline mode.  If the 
     requested number of bytes was greater than $FF, and the number of 
     bytes in the file after the newline character was read was a 
     multiple of $100, then the number of bytes reported transferred by 
     ProDOS was equal to the correct number of transferred bytes plus 
     $100.
  o  Starting with V1.2 on an Apple IIgs, stopped switching slot 3 ROM 
     space and left the determination of whether the slot or the port 
     was enabled to the Control Panel; however, there was a bug in this 
     implementation which was fixed in V1.7 and described in ProDOS 8 
     Technical Note #15, How ProDOS 8 Treats Slot 3.
  o  Updated the slot-based clock driver's year table through 1991.
  o  Added a feature which allows ProDOS 8 to search for a file named 
     ATINIT in the boot volume's root directory, to load and execute 
     it, then to proceed normally with the boot process by loading the 
     first .SYSTEM file.  No error occurs if the ATINIT file is not 
     found, but any other error condition (including the file existing 
     and not having file type $E2) causes a fatal error.
  o  Changed loader code so ProDOS 8 could be loaded by ProDOS 16 
     without automatically executing the ATINIT and the first .SYSTEM 
     file.
  o  Changed the device search process in the ProDOS 8 loader so 
     SmartPort devices are only installed if they actually exist, and 
     Disk IIs are placed with lowest priority in the device list so 
     they are scanned last.
  o  Forced Super Hi-Res off on an Apple IIgs when a fatal error 
     occurs.  (Actually, this did not work, but it was fixed in V1.7.)
  o  Inserted a patch to fix a bug in the first IIgs ROM that caused 
     internal $Cn00 ROM space to be left mapped in if SmartPort failed 
     to boot.

ProDOS 8 1.3

Warning:  This is not a stable version of ProDOS due to an illegal 
          65C02 instruction which was added.  This version can damage 
          disks if used with a 6502 processor.

  o  Changed the code that resets phase lines for Disk IIs so phase 
     clearing is done with a load instead of a store, since stores to 
     even numbered locations cause bus contention, which is major 
     uncool.  Changed the routine to force access to all eight even 
     locations, which not only clears the phases, but also forces read 
     mode, first drive, and motor off.  DOS used to do this; ProDOS had 
     not been doing it.  If L7 had been left on when the Disk II driver 
     was called and it checked write-protect with L6 high, write mode 
     was enabled.  Forcing read mode leaves less to chance.
  o  Changed deallocation of index blocks so index blocks are not 
     zeroed, allowing the use of file recovery utilities.  Instead, 
     index blocks are "flipped" (the first 256 bytes are exchanged with 
     the last 256 bytes).
  o  Since the UniDisk 3.5 interface card for the ][+ and IIe does not 
     set up its device chain unless a ProDOS call is made to it, ProDOS 
     STATUS calls are now made to the device before SmartPort STATUS 
     calls.

ProDOS 8 1.4

  o  Removed an illegal 65C02 instruction which was added in V1.3.
  o  Modified the Disk II driver so a routine that should only clear 
     the phase lines only clears the phase lines.  Also clear Q7 to 
     prevent inadvertent writes.

Warning:  The AppleTalk command, which was added in version 1.5, is 
          present as a skeleton in this version.  Unfortunately, it's 
          not a useful skeleton.  It moves a section of memory from a 
          ProDOS location to another location and transfers control, 
          totally oblivious of the fact that there is no code at this 
          address.

          Even more unfortunate, the server software that ships with 
          the Apple IIe Workstation Card is such that when the IIe is 
          booted over the network with that server software, it is 
          version 1.4 (KVERSION = 4).

          So if you boot version 1.4 from a local disk, making a $42 
          call is fatal.  See ProDOS 8 Technical Note #21, Identifying 
          ProDOS Devices, for a reliable way to identify AppleTalk 
          volumes under ProDOS 8 version 1.4.

ProDOS 8 1.5

  o  ProDOS 8 1.5 is the first version to include network support 
     through the ProDOS Filing Interface (PFI) as part of ProDOS 16 or 
     on the Apple IIe Workstation Card without booting over the server 
     (see the warning under version 1.4).  Made many changes to 
     internal routines for PFI location and compatibility at this 
     point.  Crunched and moved code for PFI booting and accessibility.
  o  Changed some strings to all uppercase internally for string 
     comparisons.
  o  Removed the generic $42 AppleTalk call (the cause of the previous 
     warning) which was introduced in V1.2, as PFI gets called through 
     the global page.
  o  Changed the ASL to clear the MLIACTV flag back to an LSR.  This 
     doesn't make nested levels of busy states possible, but always 
     clears the flag before calling interrupt handling routines that 
     check MLIACTV as described in the ProDOS 8 Technical Reference 
     Manual.
  o  If an Escape key is detected in the keyboard buffer on an Apple 
     IIc, it is removed.  This is friendly to the Apple IIc Plus, the 
     ROM of which does not remove the Escape key it uses to detect that 
     the system should be booted at normal speed.

ProDOS 8 1.6

  o  Set up a parallel pointer to correct a PFI misinterpretation of an 
     internal MLI pointer.

ProDOS 8 1.7

  o  Made a change to ensure that ProDOS 8 counts the volume's bitmap 
     before incrementing the number of free blocks.  This fixed a bug 
     where an uninitialized location was being incremented and 
     decremented, incorrectly reporting a Disk Full error where none 
     should have occurred.
  o  Changed the handling of slot 3 ROM space to that described in 
     ProDOS 8 Technical Note #15, How ProDOS 8 Treats Slot 3.
  o  Changed code to permit the invisible bit of the access byte (bit 2) 
     to be set by applications.

ProDOS 8 1.8

  o  Fixed a bug introduced in V1.3.  If an error occurs while calling 
     DESTROY on a file, the file is not deleted but the index blocks 
     are not swapped back to normal position.  If a subsequent DESTROY 
     of the same file succeeds, the volume's integrity is destroyed.  
     Now ProDOS 8 marks the file as deleted, even if an error occurs, 
     so any other errors do not cause a subsequent MLI call to trash 
     the volume.  Note that "undelete" utilities attempting to undelete 
     such a file (one in which an error occurred during the DESTROY ) 
     may trash the volume.
  o  Fixed the ONLINE call to ignore the unused low nibble of the 
     unit_num parameter when deciding how many bytes to zero in the 
     application's buffer.  This change fixes a bug which zeroed only 
     the first 16 bytes of the caller's buffer before filling them if 
     an ONLINE call was made with a unit_num of $0X, where X is non-
     zero.
  o  When loading on an Apple IIgs, ProDOS 8 now sets the video mode so 
     the 80-column firmware is not active when the ProDOS 8 application 
     gets control.
  o  Changed internal version checking between GS/OS and ProDOS 8.  
     Note that GS/OS and ProDOS 8 are still tied to each other--versions 
     that didn't come on the same disk can't be used together.  The 
     methods for checking versions were just altered.
  o  Made the backward compatibility check when opening subdirectories 
     inactive.  The test would always fail when opening a subdirectory 
     with lowercase characters in the name (as assigned by the ProDOS 
     FST under GS/OS), so the check was removed.  Note that using 
     earlier versions of ProDOS 8 with such disks causes errors when 
     trying to access files with such directories in their pathnames.
  o  Expanded the ProDOS 8 loader code to provide for more room for 
     future compatibility.
  o  On a IIgs, installs a patch into the GS/OS stack-based call vector 
     so that anyone calling GS/OS routines (like QDStartUp in ROM 03, 
     for example) gets an appropriate error instead of performing a JSL 
     into the stratosphere.

ProDOS 8 1.9

  o  New selector and dispatcher code was added for machines with 80 
     columns.  The old code is still present for machines without 80-
     column capability.

  o  Fixed two bugs involved in booting into a ".SYSTEM" program larger 
     than 38K.  First, ProDOS 8 should be able to boot into a program 
     as large as 39.75K, but was returning an error if the ".SYSTEM" 
     program was larger than 38K.  Second, when attempting to print the 
     message "*** SYSTEM PROGRAM TOO LARGE ***", only one asterisk was 
     printed.  Both these bugs are fixed.

  o  No longer requires a ".SYSTEM" file when booting.  If ProDOS 8 
     does not find a ".SYSTEM" file and the enhanced selector and 
     dispatcher code is installed, ProDOS 8 executes a QUIT call.

  o  KVERSION is still $08.

Known Bugs in ProDOS 8 1.9

  o  ProDOS 8 doesn't handle seedling sparse files correctly.  If you 
     have a seedling file (only one block, less than 512 bytes of data) 
     and use SET_EOF to grow the EOF without writing any data, the file 
     becomes a sparse seedling file.  The EOF indicates the file is a 
     sapling or tree file, but in fact only one disk block is used.  
     The storage type correctly indicates a seedling file.

     If you have such a file, and try to shrink it by setting the EOF 
     to a value that is not an even multiple of a block boundary, 
     ProDOS 8 gets confused and trashes some of the second half of the 
     real data block.

  o  If you perform a SET_PREFIX to a slash (/) followed by a 
     SET_PREFIX to a volume name not preceded by a slash, the prefix 
     gets set to the first letter of the volume name.


Further Reference
_____________________________________________________________________________
  o  ProDOS 8 Technical Reference Manual
  o  ProDOS 8 Update
  o  AppleShare Programmer's Guide to the Apple II
  o  ProDOS 8 Technical Note #21, Identifying ProDOS Devices

