局部变量，全局变量和数组

http://www.cnblogs.com/snake-hand/archive/2013/06/16/3138866.html

http://blog.youkuaiyun.com/handsomekang/article/details/41392417?utm_source=tuicool&utm_medium=referral

http://www.cnblogs.com/kaituorensheng/archive/2013/01/05/2846627.html