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Changes
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; > Changes
Changes from Arthur 1.20
========================
Here are a few major points that users and programmers may notice as
differences from Arthur 1.20. Some of these chanages are unavoidable if
progress is to occur, but some may come as a slight surprise and so it seems
worth summarising them.
ALT on the keyboard now acts as a shifting key, in line with usage on
other machines. In order to get the old behaviour, get a *-prompt
and type:
*RMKill InternationalKeyboard
This will kill the international keyboard module, removing some extra
features of RISC OS 2.00 (for international users). To get back to the
default state:
*RMReInit InternationalKeyboard
The high-resolution monochrome monitor spec has changed to a higher screen
refresh rate. Mode 22 no longer exists, mode 23 is now 1152*896 at 60 Hz.
Mode 23 can now do graphics.
When using the Wimp in mode 20 (MultiSync monitor), the operating system now
scales characters from the system font so that they have a better aspect
ratio than before, occupying 8*16 pixels on the screen. Old Wimp programs
which relied on the old 1:1 aspect ratio for characters will run
successfully as long as they do a mode change at the start of the program.
The width of window scroll and title bars has also changed, programs should
not have relied on these.
The floating point emulator is still loaded from disc, and the old one (pre
2.60) no longer works. There was a bug in the original FPE (a badly formed
module header) which happened to work for 1.20, but does not work on
subsequent versions. A new FPE is supplied on the Welcome Disc, which you
should use to replace the old on for programs such as Logisitix.
The basic editor module is no longer in the ROM, but it is provided on disc.
It must be RMLoaded before use from Basic. Depending on how you enter Basic,
it may be necessary to do this before entering the basic interpreter.
This is also true of the HardCopy module.
DeskFS: contains different things. Programs relying on its contents
may well no longer work.
The exact amount of memory freed by sequences of RMKills is not the same as
in 1.20. For this reason, boot sequences on some application packages may
require updates. In general boot sequences can be written far more
easily on RISC OS 2.00 because of the Obey file type.
The Wimp now acquires memory from the RMA as windows are created etc,
rather than reserving 32K for its own permenant use. This means that
some old Wimp programs fail to start, saying "No room to create window".
Such things are usually cured by giving the machine more RMA space
(by dragging the RMA bar in the Task Manager window) before starting
the application.
The Wimp's emulation of the environment for old applications is not
complete. Problem areas:
selected sprites are rendered incorrectly
sprites are scaled according to their mode, this used not to happen
In practice this affects very few applications.
ADFS now keeps separate owner and public access bits for each file. This
means that if a file is copied from net to ADFS to net, the access bits are
preserved. By default new files are created as WR/, and so files created on
ADFS and then copied to the net will now have access WR/ rather than WR/WR
as they did under 1.20.
*CDir (create directory) in ADFS, RAMFS and NETFS now creates unlocked
directories. Locking directories is not usually necessary, as they cannot
be deleted anyway without first deleting their contents. This change
has been implemented by performing multiple operations to the fileserver
on a *CDir, so it works with all fileservers.
*CDir on the net in 1.20 used to signal an error if the directory already
existed, it now (in line with ADFS) does not complain. This change
has been implemented by performing multiple operations to the fileserver
on a *CDir, so it works with all fileservers.
The major areas of extension of the system can be summarised as follows:
output of graphics to sprites
output to graphics to all screen modes except modes 3, 6 and 7 (Teletext)
new SpriteExtend module, provides scaled and translated sprite plotting.
new Draw module, provides thick/dotted lines with various options,
arrow heads, Bezier curves, etc.
multi-tasking in the window system: numerous major extensions.
the Obey module, somewhat like nestable Exec files.
the RAM filing system
the new ADFS disc format, which does not need compaction
and is more resilient to system crashes (by keeping
duplicate space maps etc.)
XON/XOFF protocol in the serial line driver
faster interrupt handling
overlays in Basic
The sound system no longer deals with overruns in the same way; the method
used in Arthur 1.20 could no longer be supported (ie. call fixup, do longjump
on IRQ stack) as other IRQ handlers now reenable IRQ. If an overrun occurs,
ie. Level 0 was entered with a Sound IRQ before Level 1 and the Voice
Generators had finished filling the next sound buffer, then the same buffer
is replayed again on the next buffer swap, so about one centisecond of sound
will be corrupted. Level 1 fixup code is no longer called; neither are Level
1 Fill or Level 2 called, so the centisecond of music will be delayed. In
extreme cases (VERY high video DMA overhead) this can lead to the pitch
flattening.
The run-type of Text files is now *type rather than *exec.