Floating Point means decimal point.
A bit of a simplication.
More than you want to know?:
http://en.wikipedia.org/wiki/Floating_point
A waste of time (but funny?)
http://del.icio.us/url/53db119a950dc8c8b8dfbd087cf4680e
Ignore this if it makes things more confusing:
(This ignores negative numbers)
(This uses small numbers just for explanation)
If you have a 3-digit field, three options for storing numbers:
1) Integer:
You can store 0 to 999.
You can store only the integer part of 1.2
You can't store 12000 nor .00034
You can't store 12345 nor .00056789.
2) Fixed (decimal) Point, say 2 decimal places.
You can store 0.00 to 9.99.
3) Floating Point:
Allows you to store a very large range of numbers
but at 2-digit accuracy instead of 3.
The first 2 digits will be the "mantissa", the first 2
significant digits, which will range from .00 to .99
The 3rd digit will be 4 + the exponent of 10.
The exponent can range from -4 to 5.
The equation of the value is
mantissa * 10 ^ (3rd digit - 4).
("^" means "to the power of")
You will be able to
store 0 to 99.
store 1.2 and 34000 and .00056.
store 999 and 12345 and .00056789, but not exactly.
1 stores as 105 (.10*10^1=1)
1.2 stores as 125 (.12*10^1=1.2)
10 stores as 106 (.10*10^2=10)
99 stores as 996 (.99*10^2=99)
100 stores as 107 (.10*10^3=100)
230 stores as 237 (.23*10^3=230)
1000 stores as 108 (.10*10^4=1000)
34000 stores as 349 (.34*10^5=34000)
..1 stores as 104 (.10*10^0=.1)
..00056 stores as 561 (.56*10^-3=.00056)
999 stores as 997 (.99*10^3=990) not exact
12345 stores as 129 (12*10^5=12000) not exact
..00056789 stores as 561 (.56*10^-3=.00056) not exact
In binary it's a binary point instead of a decimal point,
but the idea is the same. But .8 in binary is
..110011001100..(infinitely) as 1/3 in decimal is
..3333..(inifinitely); and there is rounding,
so there are comparing issues in floating point.
D-C Dave
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