Question

I am making an application in C# and I have hex numbers such as 0x0FF8,0xFFFA etc.

Here I want only 12 bit from right to left. Suppose I have a number as 0x0FF8.
So I just want to make operation on FF8.(12 bits), and this is signed number.

It is the decimal number is -8. In my application I have to first find whether number is negative or not? And after that its value.

I am not getting how to do it in C# efficiently as I have to do it very fast.
The number representation is as 0x0FF8= -8 please see the link http://www.swarthmore.edu/NatSci/echeeve1/Ref/BinaryMath/NumSys.html

Answer 1

erm,

To get the right twelve bits only you could do,

var right12 = 0x0FFF & yourNumber;

To find out if it negative or positive do,

var positive = yourNumber >= 0;
var absoluteValue = Math.Abs(yourNumber); // Assuming yourNumber is Int32
var low12 = 0xFFF & absoluteValue;

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This does a bitwise and against a bit mask for the twelve bits you want to keep.