> For the complete documentation index, see [llms.txt](https://calnix.gitbook.io/eth-dev/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://calnix.gitbook.io/eth-dev/reading-txn-input-data.md).

# Reading txn input data

Any transaction with data payload is meant to be addressed to a smart contract. These types of transactions usually invoke a function on smart contract.

![](/files/FtPinlzTa3XwSTaaPQRT)

The data payload is the hex data we see here. It is bytecode that the EVM will understand and execute. Let's breakdown the transaction data:

{% code overflow="wrap" %}

```bash
0xe2bbb15800000000000000000000000000000000000000000000000175150904d98ada050000000000000000000000000000000000000000000000000000000000000000

0x
e2bbb158
00000000000000000000000000000000000000000000000175150904d98ada05
050000000000000000000000000000000000000000000000000000000000000000
```

{% endcode %}

<figure><img src="/files/No3y2dPvXMIF1WzvB5Km" alt=""><figcaption></figcaption></figure>

{% hint style="info" %}
32 bytes == uint256

* 256 bits -> 64 hex characters    \[1 hex -> 4 bits]
* 1 byte -> 2 hex characters -> 8 bits
  {% endhint %}