update README with info regarding bech32m checksum changes

README.md

@@ -29,7 +29,7 @@ make test
 ### Installing prerequirements
 
 If the above doesn't work, you probably need to install some
-prerequirements. For example, on a fresh Debian Stretch system:
+prerequirements. For example, on a fresh Debian 10 ("buster") system:
 
 ```
 sudo apt-get install make gcc g++
@@ -38,16 +38,18 @@ sudo apt-get install make gcc g++
 It is worth getting the latest cmake, so install that the hard way:
 
 ```
-wget https://cmake.org/files/v3.13/cmake-3.13.2.tar.gz
-tar xzf cmake-3.13.2.tar.gz
-cd cmake-3.13.2
+wget https://cmake.org/files/v3.19/cmake-3.19.4.tar.gz
+tar xzf cmake-3.19.4.tar.gz
+cd cmake-3.19.4
 ./configure
 make 
 sudo make install
 ```
 
 Now you can again try to build libbech32.
 
+## Example Code
+
 ### C++ Usage Example
 
 ```cpp
@@ -75,6 +77,8 @@ int main() {
 }
 ```
 
+For more C++ examples, see `examples/cpp_example.cpp`
+
 ### C Usage Example
 
 ```C
@@ -113,3 +117,43 @@ int main() {
     bech32_free_bstring(bstring);
 }
 ```
+
+For more C examples, see `examples/c_example.cpp`
+
+
+## Regarding bech32 checksums
+
+The Bech32 data encoding format was first proposed by Pieter Wuille in early 2017 in
+[BIP 0173](https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki). Later, in November 2019, Pieter published
+some research regarding that an exponent used in the bech32 checksum algorithm (value = 1) may not be
+optimal for the error detecting properties of bech32. In February 2021, Pieter published
+[BIP 0350](http://www.example.com) reporting that "exhaustive analysis" showed the best possible exponent value is
+0x2bc830a3. This improved variant of Bech32 is called "Bech32m".
+
+When decoding a possible bech32 encoded string, libbech32 returns an enum value showing whether bech32m or bech32
+was used to encode. This can be seen in the exaples above.
+
+When encoding data, libbech32 defaults to using the new exponent value of 0x2bc830a3. If the original exponent value
+of 1 is desired, then the following functions may be used:
+
+### C++ Usage Example
+
+```cpp
+    /// ... as above ...
+
+    // encode
+    std::string bstr = bech32::encodeUsingOriginalConstant(hrp, data);
+
+    /// ... as above ...
+```
+
+### C Usage Example
+
+```C
+    /// ... as above ...
+
+    // encode
+    assert(bech32_encode_using_original_constant(bstring, hrp, dp, sizeof(dp)) == E_BECH32_SUCCESS);
+
+    /// ... as above ...
+```