In the source code for the CBlockHeader class, there is a field called nBits.
/** Nodes collect new transactions into a block, hash them into a hash tree,
* and scan through nonce values to make the block's hash satisfy proof-of-work
* requirements. When they solve the proof-of-work, they broadcast the block
* to everyone and the block is added to the block chain. The first transaction
* in the block is a special one that creates a new coin owned by the creator
* of the block.
*/
class CBlockHeader
{
public:
// header
int32_t nVersion;
uint256 hashPrevBlock;
uint256 hashMerkleRoot;
uint32_t nTime;
uint32_t nBits;
uint32_t nNonce;
As far as I searched in the code, I didn't found any comment for this field. But I saw the CheckBlockHeader function using the nBits field to check proof of work of the block. So I interpret that it's a representation of the difficulty for the block.
static bool CheckBlockHeader(const CBlockHeader& block, BlockValidationState& state, const Consensus::Params& consensusParams, bool fCheckPOW = true)
{
// Check proof of work matches claimed amount
if (fCheckPOW && !CheckProofOfWork(block.GetHash(), block.nBits, consensusParams))
return state.Invalid(BlockValidationResult::BLOCK_INVALID_HEADER, "high-hash", "proof of work failed");
return true;
}
Is my understanding correct?
