The Solidity codes can further undergo unit testing and integrated

testing from the test networks, and finally be deployed on the

Ethereum

mainnet

or

on

production.

We

can

visit

https://etherscan.io/ to find many transactions that are being

executed on the Ethereum network every now and then.

2.5.6 Application Binary Interface

Every contract comes with a binary interface for integration with the

front-end code as well as the other contracts that can interact with it.

The binary interface is way similar to API or Application

Programming Interface that the high level languages use to expose

their services to the external world. ABI has the information of all the

function names, input and output parameters, and Event names and

their parameters. On the REMIX browser, once we compile the code,

we can find a “Compilation Details” button, clicking on which, we can

view the details of the ABI.

2.5.7 Layout of Solidity source code

Now, let’s find out the internal details of a Solidity file. First of all, a

solidity file has a .sol extension.

2.5.7.1 SPDX License Number

On the first line in the Solidity file, we can have an optional comment

within which we have to specify the license associated with the code.

This is useful if you wish to add any copyright related information, as

follows:

// SPDX-License-Identifier: Some Identifier

If you do not wish to write any SPDX identifier, just write the

following:

// SPDX-License-Identifier: Some Identifier

However, not writing it might throw a warning message.