HP -18C Owner's Manual page 151

Here are several additional examples of formulas using conditional
expressions:
Formula:
B = I F
0::
7 <A At·m A (= 15 :
2>' A~6
: 3>::A +10) +C
Meaning: If A is greater than 7 and less than or equal to 15, then
B
=
2
x
A -;- 6
+ c.
Otherwise, B
=
3
x
A
+
10
+ c.
Formula:
I,}ALUE=F IF.:ST +1 F
0::
NOT F I RST=0: 1
~F
I RST:
(1)
Meaning: If FIRST is unequal to 0, then VALUE
=
FIRST
+
1
FIRST. If FIRST
=
0, then VALUE
=
FIRST.
9: The Formula Solver 149