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Ethereum: basics 1

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Basics: Epoch 8: Transactions

The transaction

The simplest use of a transaction is to move ethers from an address to another.
A transaction is identified by a 256 bit hash. You can check every transaction in a block explorer. If, for example, you check again my wallet balance (as explained in Balance) you'll see a list of transactions identified by a TxHash, and you can expand the data of this single transaction, that remains in the block chain forever:
An example of transaction on EtherScan
Here you can see the following information stored in a transaction:

  • from: the sender's address
  • to: the recipient's address
  • value: the value of wei transferred

Actually, from is not truly stored in the blockchain, indeed we have v, r, s, values that identify the sender's signature.
There are other data sent in a simple transaction:

  • nonce
  • gas price
  • gas limit

gas is the fuel of the Ethereum system, and it's a very important concept.

Gas Price

To make it simple, the gas is expressed in wei, but it's not part of the value.
It's the price you want to pay for the transaction to be processed by a miner.
The miner is interested in gaining much gas as possible for his computation, so prefers transactions which pay more gas.
The more gas you pay, the faster the transaction is processed.
Obviously, you want to pay less gas as possible, but if you pay too low, no miners will be interested in processing your transaction, and it will employ a lot of time.

Gas price is a market indipendent from the ethereum price, and there are sites to choose the value you need (if you want fast transactions, you pay more, if you want pay less, you'll have slower transactions.
One of these sites is Eth Gas Station

Gas Limit

The other parameter you can define in a transaction is the maximum gas (in wei) you are ready to pay for your Tx. This value is defined in the gas limit parameter.


The number of transactions sent by the sender (0, if it's only one)

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