Mac OS X、FreeBSD、 NetBSD、OpenBSD等等操作系统到底是什么关系？

Wolfram Schneider 整理了 UNIX （主要是BSD系列） 家族谱系树，看了之后是不是一目了然了呢？

谱系树使用 ASCII 字符绘制，是不是很 geeky？

First Edition (V1)
     |
Second Edition (V2)
     |
Third Edition (V3)
     |
Fourth Edition (V4)
     |
Fifth Edition (V5)
     |
Sixth Edition (V6) -----*
       \                |
        \               |
         \              |
Seventh Edition (V7)    |
            \           |
             \        1BSD
             32V        |
               \      2BSD---------------*
                \    /                   |
                 \  /                    |
                  \/                     |
                 3BSD                    |
                  |                      |
               4.0BSD                2.79BSD
                  |                      |
               4.1BSD --------------> 2.8BSD
                  |                      |
              4.1aBSD -----------\       |
                  |                \     |
              4.1bBSD                \   |
                  |                    \ |
      *------ 4.1cBSD --------------> 2.9BSD
     /            |                      |
Eighth Edition    |                   2.9BSD-Seismo
     |            |                      |
     +---- 2.10BSD
     |            |               /      |
Ninth Edition     |              / 2.10.1BSD
     |         4.3BSD Tahoe-----+        |
     |            |              \       |
     |            |                \     |
     v            |                  2.11BSD
Tenth Edition     |                      |
                  |                  2.11BSD rev #430
               4.3BSD NET/1              |
                  |                      v
               4.3BSD Reno
                  |
   *---------- 4.3BSD NET/2 -------------------+-------------*
   |                    |                      |             |
386BSD 0.0              |                      |           BSD/386 ALPHA
   |                    |                      |             |
386BSD 0.1 ------------>+                      |           BSD/386 0.3.[13]
   |     \              |                  4.4BSD Alpha      |
   |     386BSD 1.0     |                      |           BSD/386 0.9.[34]
   |                    |                  4.4BSD            |
   |                    |                    / |             |
   |                    |   4.4BSD-Encumbered  |             |
   |                 NetBSD 0.8                |           BSD/386 1.0
   |                    |                      |             |
FreeBSD 1.0          NetBSD 0.9                |           BSD/386 1.1
   |                    |           .----- 4.4BSD Lite       |
FreeBSD 1.1             |          /   /       |     \       |
   |                    |         /   /        |      \      |
FreeBSD 1.1.5       .---|--------'   /         |       \     |
   |               /    |           /          |        \    |
FreeBSD 1.1.5.1   /     |          /           |         \   |
   |             /   NetBSD 1.0 

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