decimal in c# misunderstanding?

(while trying to analyze how `decimal` works ) && after reading @jonskeet article and seeing msdn , and thinking for the last 4 hours , I have some questions : in this link they say something very simple : `1.5 x 10^2` has `2` significant figures `1.50 x 10^2` has `3` significant figures. `1.500 x 10^2` has `4` significant figures etc... ok...we get the idea. from jon's article : ``` sign * mantissa / 10^exponent ``` As usual, the sign is just a single bit, but there are 96 bits of mantissa and 5 bits of exponent ``` ^ _ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^___ ^^^^^ 1 _ 96 5 ``` ok so max mantiss val = `2^96-1 = 79228162514264337593543950335` which is : `7.9228162514264*10^28` (according to my iphone... could'nt see exponent representation in windows calc.) notice : `7.9228162514264*10^28` has 14 significant figures (according to examples above) now the part with the 5 bit in exponent is irrelevant because its in the denominator - so i need the min val which is 2^0 question #1 : msdn say : `28-29 significant digits` but according to my sample (`1.500 x 10^2` has `4` significant figures) they have 2 significant figures which is `7.9` ( 7 and 9). if msdn would have written : ``` ±79228162514264337593543950335 × 10^0 ``` i would understand this , since all significant digits are in the expression. why do they write 28-29 but display 2 ? question #2 : how will decimal representation ( mantiss && exponent) will be displayed for the value 0.5 ? the max denominator can be `2^32-1 --> 31` thanks guys. question #3 : 1+96+5 = 102 bits. msdn says : The decimal keyword denotes a 128-bit data type. ``` 128-102 = 26 ``` could understnad from article why there isnt a usage to those 26 bits