How to obtain and install the GBA BIOS.

README.md

@@ -404,6 +404,56 @@ You may also wish to delete the higan source directory.
 Installing the GBA BIOS
 -----------------------
 
+For most of the systems higan emulates,
+the console itself contains (almost) no actual software,
+so emulating the system does not require
+infringing the copyright of the hardware manufacturer.
+However,
+the Game Boy Advance is different:
+every device contains a standard library of software routines
+for [common functions games require][bios],
+often called a "BIOS"
+by analogy with the Basic Input/Output System
+used in IBM PC compatibles.
+
+For the same legal reasons that commercial games
+cannot be distributed with emulators,
+the GBA BIOS cannot be distributed with higan,
+but is required for GBA software to run.
+
+If you have a real GBA and a flashcart,
+the Internet contains many tools
+that will extract the BIOS image so it can be copied
+to your desktop computer.
+The correct GBA BIOS file is exactly 16384 bytes long,
+and has the SHA-256 hash
+fd2547724b505f487e6dcb29ec2ecff3af35a841a77ab2e85fd87350abd36570.
+
+Once you have the correct BIOS file:
+
+ 1. rename it to `bios.rom`
+      - if you're using Windows,
+        turn off "hide extensions for known file types"
+        so you don't wind up with a file called
+        `bios.rom.dat`
+        or whatever the file's original extension was.
+ 2. Copy the file into higan`s `Game Boy Advance.sys` directory,
+    alongside the `manifest.bml` file that is already there.
+      - In Windows,
+        find `Game Boy Advance.sys` in the same folder
+        as `higan.exe`
+      - In Linux,
+        find `Game Boy Advance.sys` in
+        `~/.local/share/higan/`
+
+**Note:**
+If you upgrade this version of higan to a newer version,
+make sure the `bios.rom` file
+winds up in the `Game Boy Advance.sys` directory
+of the new version.
+
+[bios]: http://problemkaputt.de/gbatek.htm#biosfunctions
+
 Importing games
 ===============