An Introduction to Blockchain, Bitcoin, Ethereum, and ICO

Blockchain is a distributed data‑storage system maintained by multiple participants, where data is stored in a chain of blocks and secured with cryptographic techniques to ensure consistency, immutability, and non‑repudiation.

Each block consists of a block header (including generation time, hash of the block body, hash of the previous block, and a random nonce) and a block body that holds the actual transaction data.

Block header records the block's characteristic values.

Block body contains the transaction data (e.g., payment records).

The linking of blocks via the previous‑block hash creates a chain where any alteration to an earlier block would be immediately detectable, similar to a game of Chinese idiom chain.

Bitcoin was the first peer‑to‑peer electronic cash system built on blockchain. It uses a proof‑of‑work mining process where miners solve computational puzzles to create new blocks, earn transaction fees, and receive newly minted bitcoins according to a halving schedule (210 million total, reward halves every 210 000 blocks).

The typical Bitcoin transaction flow includes verifying sender and receiver addresses, signing the transaction with the sender’s private key, broadcasting it to the network, miners packaging it into a block, computing a hash that meets the difficulty target, and finally adding the block to the chain.

Key questions about Bitcoin include the resource waste of mining, potential transaction congestion, storage of blockchain data, and the system’s sustainability after all bitcoins are issued.

Ethereum , created by Vitalik Buterin, extends blockchain functionality by providing a Turing‑complete virtual machine (EVM) that can execute smart contracts, enabling decentralized applications beyond simple currency.

Ethereum can be likened to an app store or a blockchain operating system, where developers deploy contracts that run on every node, and each transaction incurs a gas fee to prevent wasteful computation.

Smart contracts are programs stored on the blockchain and executed by the EVM; they are compiled to bytecode and can be written in multiple languages.

An Initial Coin Offering (ICO) is a fundraising method where investors exchange existing cryptocurrencies (like Bitcoin) for newly issued tokens of a project. While ICOs provide a third‑party notarization mechanism, they have faced regulatory crackdowns, such as China’s 2017 ban labeling them illegal financing.

The article also highlights practical aspects of the crypto ecosystem: the high cost of mining hardware (e.g., Bitmain S9 at ~15,000 CNY), profitability calculations, the ease of creating new tokens on Ethereum, and concerns about fake trading volume on exchanges.

Finally, it raises broader industry questions about how major internet companies are integrating blockchain technology into their products.