请教mod和modz的差异

shiyiming

我在SAS HELP 上看到MOD和MODZ的介绍，没有看懂，其介绍如下：
Here are some comparisons between the MOD and MODZ functions:

The MOD function performs extra computations, called fuzzing, to return an exact zero when the result would otherwise differ from zero because of numerical error.

The MODZ function performs no fuzzing.

Both the MOD and MODZ functions return a missing value if the remainder cannot be computed to a precision of approximately three digits or more.

问题一：上文中 fuzzing 是什么意思啊？
问题二：下面的例子能否解释下？
谢谢
例子：
x2=mod(.3,-.1);
put x2 9.4;
0.0000

xb=modz(.3,-.1);
put xb 9.4;
0.1000

x4=mod(.9,.3);
put x4 24.20;
0.00000000000000000000

xd=modz(.9,.3);
put xd 24.20;
0.00000000000000005551