decimal field of a number is changing when I strip off the integer field.

lets assume I am trying to separate a number into its integer and decimal fields. Ie: 159.2345 into 159 and 0.2345

When I separate the two fields, I am getting an incorrect number for the decimal field.

Dim A as double
Dim B as Integer
Dim C as double

A = 159.2345 In the debugger I can see that the decimal numbers do not extend beyond the 5
B = int (A) THE Variable value of B is correct (159)
C = A - B the Variable Value of C is incorrect (0.234499999999997)

The result for C confuses me. the thousandths and 1/10 thousandths places are no longer 45
I do not want to round C. this error ie revealing that I do not understand something.

Perhaps it is because I am mixing data types. C = A(Double) - B(Integer)
To test this theory out, I cast B into a Double but casting did not resolve my problem.

Anyone have any ideas?

I am running excel 365 home edition on W10 insider

bil

Thank you for all your replies.

Answers I read included:
* problem you are seeing is inherent in binary computers
* When you subtract numbers, there is a loss of precision
* Looks like standard, routine double precision round-off error (you would probably get the exact same
answer from any other programming language using double precision variables).

I would like to present an argument that suggests your answers are not relevant to subtraction. They could be relevant to addition, division, multipliation, but not subtraction.

Lets begin with a cursory look at the factors effecting arithmetic on computers.
software stores floating point numbers in many ways. Storage is dependent on many factors that include hardware as well as chosen algorithm for handling floating point arithmetic. Those computers with hardware floating point processors encourage one kind of number storage and those computers without hardware floating point hardware can handle storage in multiple ways because there are many algorithms to chose from.

One way, without a hardware accelerator is to separate the integer portion from the decimal.

Lets take the number I presented to you as giving me my problem. 159.1234