Variables

In Solidity, there are three different types of variables:

• State variables: These are kept in a contract storage facility permanently.

• Local variables: These retain their values while a function is running.

• Global variables: These are used to access information about the blockchain.

The state or local variable type must be declared because Solidity is a statically typed language: based on the variable type, every defined variable has a default value.

Guidelines for variable naming

• Avoid using reserved keywords: Variable names shouldn’t contain any reserved keywords. For example, we can’t use keywords like contract or function as variable names.

• Start with a letter or underscore: Variable names must begin with a letter or an underscore (_). For instance, _count, name, and _value are valid variable names.

• Include letters and characters: Variable names can also include characters and letters from a to z or A to Z. For instance, totalAmount, user_name, and myVariable are valid variable names.

• Focus on case sensitivity: Variable names are case-sensitive. This means that variables named amount and Amount are treated as distinct variables.

Declaring a variable

The data type must be specified before the access modifier when declaring a variable. For example: