资料内容：
The value stored in a variable determines that
variable's type
The type of a variable determines
• How the computer stores the data
• What operations can be done with it, and
how those operations work
• E.g. 4 + 5 returns 9
• E.g. "hello" + "world" returns
"helloworld"
Only so much you can do with basic data
types; most code we write will use data
structures
• containers that let you store multiple elements of a basic type
(or even of many basic types) in one variable
