Programs

We have mentioned Programs quite a lot of times in this tutorial. But what exactly are Programs?

The equivalent to smart contracts on Solana are Programs. Programs are nothing but executable code that is stored in Accounts marked as executable.

The way Programs differ from Smart Contracts is that Programs on Solana are stateless, i.e., they do not store the data that they are processing and acting on. Programs are stateless and all data must be passed in via separate accounts from the outside. This allows the processing of data in a parallel fashion: multiple programs can reuse the same accounts for different purposes, in different transactions.

You can imagine this parallelisation to be something similar to how functions in programming work. In programming, we can define variables to store some data. These variables can then be passed as reference to functions that make changes to these variables. In this analogy, the variables are Accounts and the functions are Programs.

Coming back to the Solscan page for a transaction with signature 3bsfEaCdbjcBvXQT3Fx85R2TvKL3KJe5kb4G8XYqUFXCBxKzemu6FV3fi2C51TBtcKpjygCfzdXsjg9dTjVxpEo5, we can start to understand what its trying to tell us.

In the transaction overview, we can checkout the block in which the transaction was executed, the fee to run the transaction, whether the transaction was successful or not and most importantly, the main actions that the transaction executes. In this case, there was a transfer of 253 SOL from wallet GFDmfhoPtZZATNxw8zyZPVYKkBZutf1zoZTbRbxDjh5E to 4tzAkc7cGTns1dsVaP18KvMkt9jEmzA1AaV3rMzgyi7f.

We can also see the same on the instruction detail. In the given transaction, only 1 instruction was executed. As it was a simple SOL transfer, the program which interacts with the transaction is the System Program, with hash: 11111111111111111111111111111111.

If we go back to the Account page on Solscan, we can see a section for Token Accounts and also see some SPL-tokens listed. Let us see what these are.