128 bit Decimal Type

computerpublic

Hello, I have some issues with the understanding of how it is possible to use a the 128 bit Decimal Type on my 64 bit computer. Somehow the logic doesn't seem to come to me. Can someone please explain how this is possible? Thank You.

Lost User

Which logic? Just declare a decimal. http://msdn.microsoft.com/en-us/library/364x0z75.aspx[^] The decimal will have that size, regardless of the bitness of your machine.

Bastard Programmer from Hell :suss: If you can't read my code, try converting it here[^]

OriginalGriff

How do you think 8 bit processors handled 16 bit integers? It's not difficult: you just have a half carry in the middle!

0x1234 + 0x6743
is worked out in 8 bits as:
0x34 + 0x43 == 0x77 plus a zero carry
and 0x12 + 0x67 + 0 == 0x79

== 0x7977

It's not done quite that way with decimals (because floating point arithmetic is a lot more complex) but that's the general idea. Think about it: you are a base ten processor: but there is no limit on how big a pair of numbers you can do arithmetic with!

You looking for sympathy? You'll find it in the dictionary, between sympathomimetic and sympatric (Page 1788, if it helps)

PIEBALDconsult

You had me at

OriginalGriff wrote:

how big a pair

PIEBALDconsult

See also: http://msdn.microsoft.com/en-us/library/system.numerics.biginteger(v=vs.110).aspx[^]

OriginalGriff

Clubs? Spades? :InnocentWhistleSmiley:

You looking for sympathy? You'll find it in the dictionary, between sympathomimetic and sympatric (Page 1788, if it helps)

PIEBALDconsult

At clubs usually. As for the other, I hesitate to use such language.

OriginalGriff

Grief! That's a term I hadn't heard or thought about for decades. I assumed that died in the 70's!

You looking for sympathy? You'll find it in the dictionary, between sympathomimetic and sympatric (Page 1788, if it helps)

PIEBALDconsult

Yeah, it's not used so much anymore. It appears in "Streets of Fire" (circa 1984) and if I recall correctly, Bill Maher used it a while back.

Lost User

It's not a type directly supported with processor instructions dedicated to it. You can look at its source[^] to see how it works (does not include the source of some math operations and so on, but shows their function names).

Ravi Bhavnani

You may be confusing addressing space with data size. A 64-bit computer can address 264 bytes. An instance of a 128 bit decimal type (located somewhere in the address space) occupies 16 bytes. /ravi

My new year resolution: 2048 x 1536 Home | Articles | My .NET bits | Freeware ravib(at)ravib(dot)com

jschell

computerpublic wrote:

Somehow the logic doesn't seem to come to me

Might help if you wrote your own class to do infinite digit integer handling. So you want a class that can take a 50 digit integer and add a different 50 digit integer to it. Each class instance represents a single number. So the add operation would look like the following. MyInt op1 = new MyInt("1000....001"); MyInt op2 = new MyInt("9000....019"); MyInt result = op1.add(op2);