Klaytn Docs
Klaytn Smart Contract
Smart contracts in Klaytn are programs that implement business logics, games, libraries, token transfers, or any type of code interacting with the Klaytn blockchain. When conditions described in the smart contract are met, the contract executes immediately. The terms within smart contracts are described in programming language; their contents data are stored as their state.
Klaytn provides several ways to write and execute smart contracts on the Klaytn network. First, Klaytn supports Solidity and maintains interoperability with Ethereum development toolkits such as Remix or Truffle. Smart contracts written in Solidity can be compiled using existing Solidity compilers and execute on Klaytn without additional work. Since Solidity is the de facto standard contract programming language in Ethereum and is backed by active communities, Klaytn supports the language to provide developers with the most familiar development environment onto which Ethereum DApp developers could easily migrate their existing work.
In the future, Klaytn plans to accommodate smart contracts written in various programming languages, in order to extend support to a broader range of potential developers and provide them with development experience they feel they're most familiar with. Going forward, Klaytn will continue to explore various programming languages that developers find interesting.

Affordable Smart Contract Execution Cost

One of the reasons that blockchains charge fees on smart contract executions is to utilize limited resources efficiently by preventing poorly or maliciously written contracts from running. That is, a blockchain platform increases the financial cost of running smart contracts intentionally (1) to induce developers to write efficient code, and (2) to deter adversaries in launching attacks by minimizing the expected financial gains. With a successful strategy, the fees charged on normal executions should be small, although the fees from malicious executions should be large. Although Ethereum’s opcode-based fee model is useful in discouraging wasting of resources, it may also dampen ordinary smart contract executions due to high gas prices on some opcodes (e.g., state write), hindering the adoption of blockchain technologies. To address this problem, Klaytn plans to use an opcode-based fixed fee model with low unit cost per opcode. This is made possible by dramatically increasing scalability of blockchain protocol.
Opcode cost is directly related to the amount of resources that the platform can use. The Ethereum state write cost is high since the storage, and the network bandwidth required to record and propagate the changed states are limited. Conversely, if a blockchain has abundant resources (e.g., CPU time, storage, network bandwidth), then the unit cost per opcode can be substantially lower than that of Ethereum, and the cost difference between opcodes can be minimized. Klaytn aims to lower opcode unit cost by vertically scaling each CN node (i.e., acquiring high-end hardware), parallelizing computation (i.e., logical scaling via service chain), and horizontally scaling physical clusters.
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