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70
PROGRAMMING THE 91008
PROGRAM
EYS
( +
)00.
Halts program execution, causing a return to the dis-
play mode; also, resets the program counter to (
+
)00
so that pressing CONT begins program execution at
When used as a program step END is the equivalent of:
STOP, GO TO,
+,
0, 0.
When used from the keyboard, END is the equivalent of:
GO TO,
+,
0, 0.
lf END is included in a program being entered from a magnetic
card, the END instruction will stop the card reader and reset the
program counter to (
+
)00. This means that anything following
the END instruction, if it is on the same page as the END in-
struction, cannot be re-entered into the calculator. For this rea-
son if the 'END' appears other than as the last required instruc-
tion on a page, or if data follows the END, then replace the END
instruction, by any other instruction, before recording the pro-
gram. When the program has been re-entered from the card
the EN9
1
instructions can be re-inserted (see CORRECTING A
PROGRAM on Page
79).
I
•
This instruction single-steps the program. This is the
only instruction on the calculator which cannot be in-
cl uded as a program step.
ln PROGRAM mode, each time STEP PRGM is pressed, the next
address tobe stepped (together with the instruction code
at
that
address) appears in the Z register. The last address stepped
(and the instruction code at that address) appears in the
X
register.
NOTE
The original contents of the Z register will reappear
when the
PROGRAM - RUN
switch
JS
switched back
to
RUN;
the onginal contents of the
X
register are
lost.
ln RUN mode,
STEP
PRGM
single-steps the program, display-
ing the contents
of X, Y, and Z registers after each step. Data
must
be entered at the proper program steps to check opera-
tion
of the program.
The use
of STEP PRGM is fully detailed
under
EDITING A PRO-
GRAM
and CORRECTING A PROGRAM (Pages 76 and follow-
ing).
Several program
instructions
do not operate as expe~ted
when the STEP PRGM key is used; these
·
are also expla1ned
under
EDITING A PROGRAM.
j
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