Unable to understand how smart contracts work

Question

I'm reading several articles about privacy in ethereum smart contracts but still I don't understand how everything in the smart contract is visible to anyone?

What does this mean?

Answer 1

On a public blockchain, all the transactions between accounts (externally controlled and smart contract) are public. You can browse each transaction of each block using tools such as EtherScan.

For example, on the picture below, you can see every data for a transaction to a smart contract (write operation) :

• Transaction Hash
• Block No
• Timestamp
• From account
• To account
• Value
• Gas
• Input data : This is the data passed to the smart contract which are totally public

Moreover, you can call read only (constant) operations for a smart contract if you have the ABI and the contract address.

pragma solidity ^0.4.0;

contract SimpleStorage {
    uint storedData;

    function set(uint x) public {
        storedData = x;
    }

    function get() public constant returns (uint) {
        return storedData;
    }
}

Here anybody can call get() to retrieve the value of storedData