This code creates a new CBlock object and populates it with transactions. It then calls the GetHash method to calculate the block hash and stores it in the `hash` variable. Example 2:c++ CBlockHeader header; // ...populate the header with block data... uint256 hash = header.GetHash(); ``` This code creates a CBlockHeader object, which is a lightweight version of the CBlock class that only contains the block header information. After populating the header with block data, it calls the GetHash method to calculate the block hash and stores it in the `hash` variable. Package library: Bitcoin Core.