When you are building a house, you may choose to install a home entertainment system. It is possible to buy a single unit that includes everything: television screen, tuner, VCR, DVD player, and speakers. Such a system is easy to install and works great if it meets your needs. A one-piece unit is not very flexible, however. You have to take the combination of features that the manufacturer provides. You probably won't be able to get high-quality speakers. If you want to install a new high-definition television screen, you have to throw away the entire unit and replace it, including the VCR and DVD player that may still be working fine. If you have a collection of records (some of you readers may remember what those are), you are out of luck.
在家建音响系统（俺房子还没买...），可以买个大而全的整套系统。但是DIY就不行了，为啥？接口不统一而且不全。如果你想换个高清电视，对不起全换了吧（还有更恐怖的，唉，仰天长叹，空悲切...)。在做IHome程序时，当时分了好几个组件，主要是为了隔离不同的功能，降低耦合度。读了大牛的话，又长了不少见识，组件可以单独更新替换哦。
A more flexible approach is to build your entertainment system out of individual components, each focused on a single functionality. A monitor displays the picture; individual speakers play the sound, and they can be placed wherever your room and ears allow; the tuner, VCR, and DVD player are each separate units, their capabilities adjusted to your videophile requirements and your budget. Instead of being locked together in a rigid fashion, you place each component where you want and hook them together with cables. Each cable has a specific kind of plug that fits into a matching port on a component, so you can't plug a speaker wire into a video output. You can hook up your old turntable if you want. When you want to upgrade your system, you can replace one component at a time without trashing the entire system and starting over. Components provide more flexibility and permit you to obtain higher quality, if you want it and can afford it.
更灵活的方式是通过独立的组件构建出灵活的音响系统（wow，DIY！原来世界上道理都是一至的）。本人来看，组件的划分至关重要，否则上述优势会烟消云散。设计组件时有一个根本原则：对自己负责，不要多管闲事。
