solana - getting started

 https://docs.solana.com/getstarted/hello-world

Best to start using this link to work with your hello world app

https://beta.solpg.io/

Run to get some credit for deploying application in your devnet. 

solana airdrop 2 

Solana app

use solana_program::{

    account_info::AccountInfo,

    entrypoint,

    entrypoint::ProgramResult,

    pubkey::Pubkey,

    msg,

};

// declare and export the program's entrypoint

entrypoint!(process_instruction);

// program entrypoint's implementation

pub fn process_instruction(

    program_id: &Pubkey,

    accounts: &[AccountInfo],

    instruction_data: &[u8]

) -> ProgramResult {

    // log a message to the blockchain

    msg!("Hello, world!");

    // gracefully exit the program

    Ok(())

}

Client app

// Client

console.log("My address:", pg.wallet.publicKey.toString());

const balance = await pg.connection.getBalance(pg.wallet.publicKey);

console.log(`My balance: ${balance / web3.LAMPORTS_PER_SOL} SOL`);

// create an empty transaction

const transaction = new web3.Transaction();

// add a hello world program instruction to the transaction

transaction.add(

  new web3.TransactionInstruction({

    keys: [],

    programId: new web3.PublicKey(pg.PROGRAM_ID),

  }),

);

// send the transaction to the Solana cluster

console.log("Sending transaction...");

const txHash = await web3.sendAndConfirmTransaction(

  pg.connection,

  transaction,

  [pg.wallet.keypair],

);

console.log("Transaction sent with hash:", txHash);