Their bounded nature also provides users with context about how the current settings fit within the allowable ranges, and eliminates the chance that a user will make an invalid entry (because no musician wants to be stopped by an error dialog).

• 这种有界的特性同时也向用户表明了使用情境，要输入的值必须在允许的范围内，从而消除了用户可能输入非法数值的可能（因为没有音乐人会喜欢错误对话框阻止其工作）。