哎呀，一个名字而已。
原文链接：https://blogs.msdn.microsoft.com/oldnewthing/20040122-00/?p=40963
If you go through the history of DirectX, you’ll see that there is no DirectX 4. It went from DirectX 3 straight to DirectX 5. What’s up with that?
回顾DirectX的历史，你会发现并没有DirectX 4的存在，从DirectX 3就直接蹦到DirectX 5了，这其中发生了什么事呢？
After DirectX 3 was released, development on two successor products took place simultaneously: a shorter-term release called DirectX 4 and a more substantial longer-term release called DirectX 5.
DirectX 3发布之后，有两个继任版本的开发同时启动：一个短期改进版本，称作DirectX 4，以及一个相对来说更加充实的长期发行版，称作DirectX 5。
But based on the feedback we were getting from the game development community, they didn’t really care about the small features in DirectX 4; what they were much more interested in were the features of DirectX 5. So it was decided to cancel DirectX 4 and roll all of its features into DirectX 5.
不过，基于来自游戏开发社区的反馈，开发者们并不怎么在意DirectX 4中的那些小改进，而是对DirectX 5所带来的新功能更加感兴趣。所以后来DirectX 4就被取消了，所有在DirectX 4中的新功能都被直接带进了DirectX 5中。
So why wasn’t DirectX 5 renamed to DirectX 4?
那么，为什么DirectX 5没有被改名为DirectX 4呢？
Because there were already hundreds upon hundreds of documents that referred to the two projects as DirectX 4 and DirectX 5. Documents that said things like “Feature XYZ will not appear until DirectX 5”. Changing the name of the projects mid-cycle was going to create even more confusion. You would end up with headlines like “Microsoft removes DirectX 5 from the table – kiss good-bye to feature XYZ” and conversations reminiscent of Who’s on First:
因为此时已经有成百上千的文档开始称呼这两个版本为DirectX 4和DirectX 5了，许许多多类似『特性XYZ在DirectX 5之前将不会出现』之类的内容已经落在了白纸黑字上。在这个节骨眼上改名，只会造成更多的困惑，后果可能包括类似《微软将DirectX 5从台面上移除了——与特性XYZ说再见》之类的大标题文章，以及像下面这种『先有蛋还是先有鸡』的怀旧讨论：
“I have some email from you saying that feature ABC won’t be ready until DirectX 5. When do you plan on releasing DirectX 5?”
『我收到一些邮件说特性ABC直到DirectX 5才会出来，你们准备什么时候发布DirectX 5呢？』
“We haven’t even started planning DirectX 5; we’re completely focused on DirectX 4, which we hope to have ready by late spring.”
『DirectX 5连草稿都还没打呢，我们现在是在专注于DirectX 4，今年春天晚些时候大概就能上线了。』
“But I need feature XYZ and you said that won’t be ready until DirectX 5.”
『可是我需要特性XYZ，然后你们说直到DirectX 5这个特性才能出来。』
“Oh, that email was written two weeks ago. Since then, DirectX 5 got renamed to DirectX 4, and DirectX 4 was cancelled.”
『噢，那封邮件是两个星期前写得了，在那之后，DirectX 5已经改名叫DirectX 4了，原本的DirectX 4已经被取消了。』
“So when I have a letter from you talking about DirectX 5, I should pretend it says DirectX 4, and when it says DirectX 4, I should pretend it says ‘a project that has since been cancelled’?”
『你的意思是说，如果我手里有封邮件讨论的是DirectX 5，我应该假装它在说的是DirectX 4，然后当谈及DirectX 4的时候，我应该理解为这指的是一个已经被取消了的项目？』
“Right, but check the date at the top of the letter, because if it’s newer than last week, then when it says DirectX 4, it really means the new DirectX 4.”
『没错，不过也得注意一下邮件顶上的日期，因为如果邮件是晚于上周发出的，那提到DirectX 4的时候就真的指的是新的DirectX 4了。』
“And what if it says DirectX 5?”
『那如果说DirectX 5的话？』
“Then somebody screwed up and didn’t get the memo.”
『那肯定是有人搞错了，没收到我们的备忘录。』
“Okay, thanks. Clear as mud.”
『吼，谢了，解释得真他喵的详细。』
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