c++ 复习
declaration definition

When a variable is defined,it is also declared. The other way is not true.

Syntax: Defining Several Variables of the Same Type at Once
<data-type> <identifier1>, <identifier2>, · · · ;
Examples
int radius, num of words;
char choice, gender, pass or fail;
When a variable is defined, the compiler allocates memory for
it.
The amount of memory is equal to the size of its data type.