RegisterClass和RegisterClassEx有什麼差別？引言不同之處：相關代碼片：

經過一番查找和測試，終于找到了答案：

The RegisterClass function has been superseded by the RegisterClassEx function. You can still use RegisterClass, however, if you do not need to set the class small icon. In addition,their parameters are different.

E文看不太懂，經過測試就是一個參數的差別，如果使用RegisterClassEx 則WNDCLASSEX的hIconSm參數是必須設定的。