Hardware manual

Operating System Change History
This file contains an inverse chronological listing of changes to the Alto operating system.
The "normal way" to install a new operating system is to retrieve a copy of the files NewOS.Boot,
Sys.Syms, Sys.Errors and Sys.Bk that are being distributed. Say "Install NewOS.boot" to the Exec, answer
the configuration questions and then delete NewOs.Boot.
Version 19/16 -- December 15, 1980
Additions: The major addition is that you can now erase a disk and format it to use 14 sectors per cylinder
on D0s and Dorados. It is not possible to extend a 12 sector file system to 14 sectors "in place"; you must
save your files, erase the disk and restore them.
Changes: [BFSInit] The OS refuses to boot when only one disk of a double disk file system is spinning. It
can also detect certain other blunders like DP1 containing a single disk file system rather than the second
half of the filesystem starting on DP0. It is not possible to detect all bad cases. [KeyStreams] the static
kbTransitionTable is not exported to users who wish to modify the OS’s treatment of the keyboard.
[DspStreams] it used to be that character codes below 40b unconditionally called the stream scroll
procedure. Now, if the character has a non-zero width or height it is displayed. Only characters with zero
width and height (CR and LF in particular) call scroll.
Version 18/16 -- May 5, 1980
Additions: The major addition is that you can now extend a file system by reinstalling the OS. A single
model 31 file system can be extended to a double model 31, a single model 44 or a double model 44, and a
single model 44 can be extended to a double model 44. This is accomplished by a subdialog of the ’long
installation dialog’.
Changes: [Calendar] D0s and Dorados now use Alto I clock format. [Dirs] A bug in the ’CompareFn’
feature has been fixed. [BFS] ’return on check error’ is handled better. [InOutLd] Disk error recovery
during InLd and OutLd has been improved. [DiskStreams] A bug in FilePos, introduced in OS17 and
responsible for problems with long files in FTP, has been fixed. CleanupDiskStream now does the proper
thing if a file is extended to a multiple of the page size and then trimmed back by less than a page.
[DisplayStreams] EraseBits is much faster now because it uses BitBlt. [BfsMl] BitBlt calls Swat if the BBT
starts at an odd address.
Version 17/16 -- September 9, 1979
The most significant improvements are that the DSK object has been extended to permit disk-independent
operation at the DoDiskCommand/GetCb level; procedures have been added to scan a disk stream at full
disk speed; and the directory lookup procedures have been modified to take advantage of these facilities
and thereby improve performance substantially. To make way for these improvements, all support for file
version numbers (a little-used feature) has been removed.
Incompatibilities are confined to those programs that create DSK objects, since several of the OS routines
now expect to be passed the extended versions. Programs that include the TFS must be reloaded with the
latest release of TFS; they will then run under OS 17 or OS 16. Programs that include BFSInit must be
reloaded with the OS 17 version of BFSInit; they will then not work under previous OS releases. Of the
standard Alto subsystems, FTP falls into the first category and Neptune in the second.
In the DSK object, the fields fpDiskDescriptor, driveNumber, retryCount, and totalErrors have moved,
and fpSysLog has been deleted; it is believed that no existing programs are affected by this.
Additions: [BFS] the DSK object is extended to include generic procedures InitializeDiskCBZ,
DoDiskCommand, GetDiskCb, and CloseDisk, and constants lengthCB and lengthCBZ. The CBZ
Alto Operating System May 5, 1980 33
For Xerox Internal Use Only -- December 15, 1980