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SC4.html
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<HTML>
<HEAD><TITLE>SC4 file format</TITLE></HEAD>
<BODY BGCOLOR="#ffffff" BACKGROUND="bkground.jpg">
<H1 ALIGN="Center">SC4 File Format</H1>
<H5> <A HREF="index.html">Back to RCT home</A> </H5>
<P> The SC4 file format is essentially identical to the <A HREF="SV4.html">SV4 file format</A>. There are some minor differences.
There is one major difference introduced with the first expansion pack. An
additional encryption method was added. This was apparently intended to impede
independent developers from creating a scenario editor. It serves no
programmatic purpose that I can tell. Here is a description of the additional
processing needed to inspect SC4 files that are intended for the expansion
pack(s). </P>
<P> 1) Load the file into memory and perform the usual RLE decoding. </P>
<P> 2) perform an "<B>XOR with 9C</B>" on every byte from 60018 to
1F8353. </P>
<P> 3) perform a "<B>rotate-right-by-3</B>" on the <I>second byte</I>
and then a "<B>rotate-left-by-9</B>" on every DWORD from 60018 to
1F8350 </P>
<P> To go from SV4 to SC4, reverse the above process. (untested) Note: remember
the <A HREF="checksum.html">checksum</A> values. </P>
<P> Here are the <A HREF="scenarios.html">scenario assignments</A>. </P>
</BODY>
</HTML>