Every Apple IIGS user needs at least one complete system disk. This disk is
shipped with every Apple IIGS system, and is provided on an 800K, double-
sided, 3.5 inch disk; the complete set of files will not fit on a 5 1/4" disk.
CONTENTS OF A COMPLETE APPLE IIGS SYSTEM DISK
---------------------------------------------
DIRECTORY/FILE DESCRIPTION
-------------- -------------------------------------------------------
PRODOS A routine that loads the proper operating system and
selects an application, both at boot time and whenever an
application quits.
SYSTEM/ A sub-directory containing the following files:
P8 ProDOS/8 operating system kernel and loader
P16 ProDOS/16 operating system kernel
LOADER The Apple IIGS System Loader
START The Apple IIGS Finder
LIBS/ a sub-directory containing the standard system libraries
TOOLS/ a sub-directory containing all RAM-based tools
FONTS/ a sub-directory containing all fonts
DESK.ACCS/ a sub-directory containing all desk accessories
SYSTEM.SETUP/ a sub-directory containing system initialization programs
TOOL.SETUP a load file containing patches to ROM and a program to
install them. This is the only required file in the
SYSTEM.SETUP sub-directory; it is executed before any
others in the sub-directory
BASIC.SYSTEM The Applesoft BASIC system interface program
These are all of the programs that come on a standard and complete System
disk. In many cases, however, an application will not need all of these
files, and some may be removed. The following is a list of the required
files, and a short description of when it is safe to remove the others:
DIRECTORY/FILE REQUIRED/(REQUIRED IF...)
-------------- ---------------------------------------------------------
PRODOS required
SYSTEM/ required
P8 (required if the application is ProDOS/8-based)
P16 required
LOADER required
START (required if the application works from the Finder)
LIBS/ (required if the application uses the standard libraries)
TOOLS/ (required if the application needs RAM-based tools)
FONTS/ (required if the application needs fonts)
DESK.ACCS/ (required if the application supports desk accessories)
SYSTEM.SETUP/ required
TOOL.SETUP (required if the application uses ROM-based tools)
BASIC.SYSTEM (required if the application is written in Applesoft)
SYSTEM STARTUP
--------------
Disk blocks 0 and 1 on an Apple IIGS system disk contain the startup (boot)
code. They are identical to the boot blocks on Apple IIe/IIc system disks.
This allows ProDOS system disks to boot on an Apple IIGS, and it also means
that the initial part of the ProDOS/16 bootstrap procedure is identical to
the procedure for ProDOS. For a system disk with a volume name of /SYS, the
boot process is outlined as follows:
1. The boot code searches the disk's volume directory for the first file
named /SYS/PRODOS with the file type $FF.
2. If the file is found, it is loaded and executed at location $2000 of
bank $00. If it is not found, then a message stating that PRODOS cannot
be found on the disk is displayed.
On an Apple IIe/IIc system disk, the file named PRODOS is the ProDOS
operating system. On an Apple IIGS system disk, however, this PRODOS file is
not the operating system itself; it is an operating system loader and
application selector. When it receives control from the boot code,
/SYS/PRODOS on the Apple IIGS performs the following tasks:
3. It relocates the part of itself name PQUIT to an area in memory where
PQUIT will reside permanently. PQUIT contains the code required to
terminate one program and start another.
4. /SYS/PRODOS loads the ProDOS/16 operating system kernel.
5. Using ProDOS/16 calls, /SYS/PRODOS loads the System Loader.
6. /SYS/PRODOS performs any necessary boot initialization of the system
by executing the files in the sub-directory /SYS/SYSTEM/SYSTEM.SETUP.
If there is a file named TOOL.SETUP in that sub-directory, it is executed
first -- it loads RAM-based tools and RAM patches to ROM-based tools.
Every file in the sub-directory /SYS/SYSTEM/SYSTEM.SETUP must be an Apple
IIGS load file of type $B6. /SYS/PRODOS loads it and makes a JSL to each
file in turn; when the file returns with an RTL, /SYS/PRODOS unloads it
from memory.
7. Now /SYS/PRODOS selects which program to run.
a. It first searches for a type $B3 file named /SYS/SYSTEM/START.
Typically, that file is the Apple IIGS Finder, but it could be any
Apple IIGS system program. If START is found, it is selected.
b. If there is no START file, /SYS/PRODOS searches the boot volume
directory for the first file that is either (1) a ProDOS system
program (type $FF with the filename extension .SYSTEM), or (2) a
ProDOS/16 system program (type $B3 with the filename extension
.SYS16). Whichever is found first is selected.
Note: If a type $FF file is found first, but the ProDOS operating
system (file /SYS/SYSTEM/P8) is not on the system disk, /SYS/PRODOS
will then search for and select the first ProDOS/16 system program.
c. If /SYS/PRODOS cannot find a file to execute, it will bring up an
interactive routine that prompts the user for the filename of a
system program to load.
8. Finally, /SYS/PRODOS passes control to an entry point in PQUIT. It is
PQUIT, not /SYS/PRODOS, that actually loads and executes the selected
program.