Subract bug or limitation

[IDILIO]

I have two values with exactly 1 unit of difference, by example (X+1 and X+2), when I subtract one other number (Y) from the others the results are not with exactly 1 unit of differece ((X+2-Y) and (X+1-Y) don't have exacly one 1 unit of difference), there are some changes in some decimal numbers. In the VI attached the 18th number after the , is different. All the controls/indicators have the same representation/precision. This seams to apens only when i add 1. (and if subtract one from another the result is 1)

Can someone explain the reason this appens?

Very strange...

See example attached

[Ben · Accepted solution]

Please see Greg McKaskle's discusion of epsilon for an explanation of what you are seeing.

Ben

[johnsold]

This is the well known result of the finite representation of numbers in the computer.  For a Double the representation is 64 bits containing sign, mantissa, and exponent. Some numbers displayed to 16-18 digits in decimal form cannot be exactly represented in this binary format.  The result is what you see.

There are many posts in the Forum regarding this.

Lynn 

[IDILIO]

Ok. Thank you for the confirmation.

I didn't get to find answer in forum because i didn't know exactly how/what to search.