A variable is an easy-to-use placeholder that refers to the computer’s memory address.
Each variable in Swift specifies a specific type that determines how much memory the variable takes up, and different data types also determine the range of values that can be stored.
In the previous chapter, we have introduced basic data types, including integer Int , floating-point Double and Float , Boolean type Bool, and string type String . In addition, Swift also offers other more powerful data types such as Optional , Array , Dictionary , Struct , and Class .
Next we will show you how to declare and use variables in Swift programs. Variable declaration means telling the compiler where in memory to create how much storage space for the variable. 9.5.1. Variable declaration #