Account Types

In Solana, accounts can be categorized into two types: executable and non-executable. An executable account functions similarly to a smart contract in Ethereum; it contains code that cannot be altered once deployed. Conversely, non-executable accounts serve as storage, holding mutable variables and individual assets.

Account Memory Allocation

Once the memory size of a Solana account is established, it cannot be modified.

Owner and Holder

In this context, the individual who possesses the account's private key is referred to as the holder. The term "owner" denotes the program authorized to modify an account's data. Every account within Solana has an owner, with the default being Solana's System Program. This means that only the System Program can adjust the SOL balance in your account. To clarify this point, let's examine a SOL transfer:

When you create a new account in Solana to serve as your SOL wallet, you hold the private key, making you the account holder. However, you cannot independently modify data within your account. Instead, the System Program acts as the account owner and executes any necessary changes. For instance, if you wish to transfer 1 SOL to another account, you would sign an instruction with your private key, which is then sent to the System Program. The System Program verifies the signature and, upon successful confirmation, deducts 1 SOL from your account and credits it to the recipient.

Program Data Storage

In Solana, smart contracts are termed "programs." As previously mentioned, these accounts store executable code and are immutable. But how does a Solana program maintain its state? Rather than storing data within the program itself, it is housed in separate storage accounts, which designate the executable accounts as owners. For example, if you develop a program that counts its invocations, you would need to create an additional account owned by your program to track the count. Each time the program is executed, it accesses the storage account, retrieves the current count, increments it, and updates the storage account accordingly.

Rent Mechanism

For storage accounts, users must maintain a minimum balance of lamports (the smallest unit in SOL) to keep their accounts active. These lamports are paid to validators as rent. If the lamports drop to zero, the account is removed from the blockchain.