View, constant, and pure functions

Solidity provides special modifiers for functions, such as view, pure, and constant. These are also known as state mutability attributes because they define the scope of changes allowed within the Ethereum global state. The purpose of these modifiers is similar to those discussed previously, but there are some small differences. This section will detail the use of these keywords.

Writing smart contract functions helps primarily with the following three activities:

• Updating state variables
• Reading state variables
• Logic execution

The execution of functions and transactions costs gas and is not free of cost. Every transaction needs a specified amount of gas, based on its execution, and callers are responsible for supplying that gas for successful execution. This is true for transactions or for any activity that modifies the global state of Ethereum.

There are functions that are only responsible for reading and returning the...