Edited ch09.asciidoc with Atlas code editor

ch09.asciidoc

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 === Introduction
 
-The blockchain data structure is an ordered, back-linked list of blocks of transactions. The blockchain can be stored as a flat file, or in a simple database. The Bitcoin Core client stores the blockchain metadata using Google's LevelDB database. Blocks are linked "back," each referring to the previous block in the chain. The blockchain is often visualized as a vertical stack, with blocks layered on top of each other and the first block serving as the foundation of the stack. The visualization of blocks stacked on top of each other results in the use of terms such as "height" to refer to the distance from the first block, and "top" or "tip" to refer to the most recently added block.
+((("bitcoin", "blockchain technology", id="BCblocktech09")))The blockchain data structure is an ordered, back-linked list of blocks of transactions. The blockchain can be stored as a flat file, or in a simple database. The Bitcoin Core client stores the blockchain metadata using Google's LevelDB database. Blocks are linked "back," each referring to the previous block in the chain. The blockchain is often visualized as a vertical stack, with blocks layered on top of each other and the first block serving as the foundation of the stack. The visualization of blocks stacked on top of each other results in the use of terms such as "height" to refer to the distance from the first block, and "top" or "tip" to refer to the most recently added block.
 
 Each block within the blockchain is identified by a hash, generated using the SHA256 cryptographic hash algorithm on the header of the block. Each block also references a previous block, known as the _parent_ block, through the "previous block hash" field in the block header. In other words, each block contains the hash of its parent inside its own header. The sequence of hashes linking each block to its parent creates a chain going back all the way to the first block ever created, known as the _genesis block_.
 
@@ -406,4 +406,4 @@ $ bitcoin-cli -regtest getbalance
 
 Bitcoin's various blockchains (+regtest+, +segnet+, +testnet3+, +mainnet+) offer a range of testing environments for bitcoin development. Use the test blockchains whether you are developing for Bitcoin Core, or another full-node consensus client; an application such as a wallet, exchange, ecommerce site; or even developing novel smart contracts and complex scripts.
 
-You can use the test blockchains to establish a development pipeline. Test your code locally on a +regtest+ as you develop it. Once ready to try it on a public network, switch to +testnet+ to expose your code to a more dynamic environment with more diversity of code and applications. Finally, once you are confident your code works as expected, switch to +mainnet+ to deploy it in production. As you make changes, improvements, bug fixes, etc., start the pipeline again, deploying each change first on +regtest+, then on +testnet+, and finally into production.
+You can use the test blockchains to establish a development pipeline. Test your code locally on a +regtest+ as you develop it. Once ready to try it on a public network, switch to +testnet+ to expose your code to a more dynamic environment with more diversity of code and applications. Finally, once you are confident your code works as expected, switch to +mainnet+ to deploy it in production. As you make changes, improvements, bug fixes, etc., start the pipeline again, deploying each change first on +regtest+, then on +testnet+, and finally into production.((("", startref="BCblocktech09")))