>Hi,
>
>this is the rule:
>
>If field is a coefficient for moltiplication, you can use double.
>
>If you use field on sum, double it must be forgotten.
>
>Numeric field on VFP they are implements in not efficient way, but if you sums a million values, you will not have been strange result.
>
>Currency is only numeric field sure.
>
>Fabio

Currency is the only one for sure ???
OK your tests modified a bit :

CREATE CURSOR TEST (v Y)
APPEND BLANK
FOR I=1 TO 10000
 REPLACE v WITH v+0.00003
NEXT
? TRANSFORM(v)
? TRANSFORM(v,'@^')
? v=3
? v=3.00000000000
* OK v is 3.
* No! v isn't 3.
? v=3.000000000000
? TRANSFORM(v+0.000000000000000)
? (v-3)*10^15


CREATE CURSOR TEST (v B)
APPEND BLANK
FOR I=1 TO 100
 REPLACE v WITH Round(v+0.03,4)
NEXT
? TRANSFORM(v)
? TRANSFORM(v,'@^')
? v=3
? v=3.00000000000
* OK v is 3.
* No! v isn't 3.
? v=3.000000000000
? TRANSFORM(v+0.000000000000000)
? (v-3)*10^15

I think what you showed wasn't a prolem of VFP but IEEE 754 specification.
Cetin