Here’s a little bit of code:

REPORT.

DATA a TYPE f.
DATA b TYPE f.
a = '0.1'.
b = '0.2'.
DATA c TYPE f.
c = a + b.
WRITE / c.

Output is… 3,0000000000000004E-01 (i.e. 0.300 000 000 000 000 04)

Add a couple more WRITE statements and you might begin to see what’s going on.

1.0000000000000001E-01
2.0000000000000001E-01
3.0000000000000004E-01

For a full explanation (and what put me onto this) see here. It’s kind of obvious, once you think about, but it never really occured to me!