Why NULL is 0

[ark at alice.UUCP]

In article <10229 at steinmetz.steinmetz.ge.com>, davidsen at steinmetz.UUCP writes:

> People (usually ;>) have no problem with the idea the while assigning a
> zero to a float gives it the vaule 0.0, in most implementations the
> float value does not have all bits set to zero.

I am overwhelmed by curiosity.  Can you give me examples of
three machine architectures in which the floating-point value
0 does not have all its bits set to zero?