EVM vs. SVM: Smart Contracts

• Programs process instructions received from users or other programs.
• All programs do not maintain state. In other words, the data used by programs is sent to separate accounts through instructions.
• The program itself is stored in an executable checked account.
• All programs are owned by the BPF Loader and executed by the Solana Runtime.
• Developers typically write programs in Rust or C++. However, any language targeting LLVM and BPF backend can be chosen.
• All programs have a single entry point where instruction processing occurs (i.e., process_instruction). The following parameters are always included:
• program_id: pubkey,
• accounts: array,
• instruction_data: byte array

Unlike most other blockchains, Solana completely separates data and code. All data that programs interact with is stored in separate accounts and is called through instructions.

This model allows for comprehensive single programs to operate through various accounts without the need for additional deployments. A common example of this pattern can be seen between Native and SPL Programs.

Native programs and the Solana Program Library (SPL)

Solana has many programs that serve as core building blocks for on-chain interactions.

These programs are divided into Native Programs and Solana Program Library (SPL) Programs.

Native Programs provide the foundational functionality required to operate validators. One of the most well-known programs among these is the System Program, responsible for managing new accounts and transferring SOL between two groups.

SPL Programs support various on-chain activities, including token creation, exchange, lending, stake pool generation, and on-chain name services. The SPL Token Program can be invoked directly through the CLI. Other programs, like the Associated Token Account Program, are typically configured as custom program

Writing Programs

Programs are typically developed in Rust and C++. However, you can develop in any language targeting LLVM and BPF backend. Recent efforts by Neon Labs and Solang make EVM compatibility possible, allowing developers to write programs in Solidity.

Most Rust-based programs follow the architecture below:

Recently, Anchor has emerged as a framework for developing programs. Anchor reduces boilerplate and simplifies (de)serialization handling, similar to Ruby on Rails but for Rust-based programs. Programs are typically developed and tested in the Localhost and Devnet environments before being deployed to Testnet and Mainnet.

Solana supports the following environments:

Once deployed to an environment, clients can interact with on-chain programs through RPC connections to each cluster.

Deploying Programs

Developers can deploy programs via the CLI as follows:

solana program deploy <PROGRAM_FILEPATH>

When a program is deployed, it is compiled into an ELF shared object (including BPF bytecode) and uploaded to the Solana cluster. Programs exist inside an account except when they are marked as executable and allocated to the BPF Loader. The account's address is used as the program_id to reference the program in all transactions.

Solana supports multiple BPF Loaders, including the recent Upgradable BPF Loader. BPF Loaders are responsible for managing program accounts and making this possible through the program_id for clients.

All programs have a single entry point where instruction processing occurs (i.e., process_instruction). The parameters always include:

• program_id: pubkey
• accounts: array
• instruction_data: byte array

Once called, programs are executed by the Solana Runtime.

Summary

• The Program in Solana corresponds to 'Executable account' on the Solana blockchain.
• The concept of smart contracts in Ethereum aligns with the concept of programs in Solana.
• Solana enables anyone to issue tokens without the need to deploy additional contracts.