Big Screen INIT

What is it?
	The Big Screen INIT is a program which allows you to use a much larger screen bitmap on your ordinary Macintosh.  It features selectable screen sizes, and automatic scrolling to any region on the virtual screen bitmap.

How do you install it?
	The program is very simple to install and use.  Simply place a copy of the file named Big Screen INIT in the System Folder of your boot disk.  If, at any time, you want to get rid of it, simply remove it from the System Folder.

How do you use it?
	Now, every time that you boot your Macintosh, you will be asked if you would like to use the large screen or the normal screen.  There are also two text boxes where you can type in the size of the virtual screen bitmap you want to use (the default is 640 by 1200 pixels).
	After you load the program, your Macintosh operates as usual, with the single exception of the effective screen size.

What are the requirements to run this program?
	All you need is either a Macintosh 512K Enhanced or a Macintosh Plus and this program.  The Big Screen INIT will use up some memory to store the new, large bitmap;  the default 640 by 1200 pixel virtual screen bitmap uses up about 100K of memory, and the larger the bitmap, the more memory used.

Are there any compatibility problems?
	This program should work with all programs that adhere to the guidelines established in Inside Macintosh.  Programs which write to the screen memory directly, rather than using Quickdraw, probably will not work.  The Macsbug debugger definitely cannot be used with this program.  FullPaint seems to work, but it disables the Big Screen INIT until the Mac is rebooted.  Also, this program will not work on the Macintosh II until sometime in the summer of 1987.

How does it work?
	At boot time, the Macintosh looks in the System Folder for any files of type INIT, and then executes each INIT resource within each of those files.  The Big Screen INIT is one of those files, and its loader program is executed.  If you choose to use the larger screen, the loader program allocates some permanent memory below the Macintosh display screen memory, and places a copy of the code that does the real work there.  This code allocates some more permanent memory for the virtual screen bitmap, patches a few strategic Toolbox ROM routines, and then returns control to the normal Macintosh startup program.  The patches redirect all screen operations to this virtual screen bitmap;  every operation generates an update rectangle which is then plotted on the real Macintosh screen every sixtieth of a second.
	Note:  You can change the default screen size by using the resource editor to modify the text items  #7 and #9 in DITL #128 in the the Big Screen INIT file.

How much does this program cost?
	This program is offered as shareware;  you can make as many copies of it as you like, and give it to interested friends, etc.  If you like this program, and wish to support the development of other shareware programs, please send $5 to:

Kurt J. Hebel
252 ERL
103 S. Mathews
Urbana, Illinois
61801-2977

Version information:

1.00	Released April 1, 1987.
1.01	Fixes plotting in Apple's Smalltalk-80 for the Macintosh.  Note that Smalltalk versions 0.3 and lower have problems when screen size exceeds 32 kilobytes.  This version also attempts to fix problems associated with the use of the alternate sound and screen buffers.
1.02	Fixes some plotting problems when using the Finder.  Removed some unnecessary code.
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