HP 9100B Operating & Programming Manual page 33

THE KEYBOARD
ENTRY KEYS
The example following serves three functions:
illustrates the use of the CLEAR X key;
illustrates the d1fference between terminated and unter-
minated numbers;
provides a valuable 'time-saving' hint.
A long IIst of numbers is to be added; as each number is added,
the accumulative total appears in the
Y
register and the last
number entered appears in the
X
register. Halfway through the
Iist, the person operating the calculator is distracted; when he
returns to the Iist he is embarrassed as he cannot remember
whether or not the number in X has been added to the total in
Y. The example shows how the CLEAR X key can be used to
determine this without repeating the complete Iist.
EXAMPLE:
Add -, -, 7, 32, 4, -, -, etc.
operator interrupted here
(assume that the numbers before 7 total 456)
STEP KEY
1
CLEAR
2
4
3
5
4
6
5
t
'155
~ y
(accumulative total)
this sets up the situation described; the next num-
bers to be added are 7 and 32:
STEP
KEY
6
7
7
~
X,
7
+
7
~ X, '153
~
8
3
9
2
32
~ X, '153
~
the operator
is
interrupted and now he cannot recall
w~ether
or not the
+
key
was
pressed.
Ta
determine
th1s:
~Y
y
STEP
10
KEY
1
321
~
X
I
'153
~
y
CONTINUED
23