HP 15c Manual

							 Section 5: The Display and Continuous Memory 61 
 
 
Digit Separators 
The  HP-15C is set  at  power-up  so  that  it  separates  integral  and  fractional 
portions  of  a  number  with  a  period  (a  decimal  point),  and  separates  groups 
of  three  digits  in  the  integer  portion  with  a  comma.  You  can  reverse  this 
setting  to  conform  to  the  numerical  convention  used  in  many  countries.  To 
do  so,  turn  off  the  calculator.  Press  and  hold =,  press  and  hold ., 
release =,  then  release . (= / .).  (Repeating  this  sequence  will 
set the calculator to the previous display convention.) 
Keystrokes Display 
12345.67 12,345.67 
= / . 12.345.6700 
= / . 12,345.6700 
Error Display 
If  you  attempt  an  improper  operation—such  as  division  by  zero—an  error 
message  (Error followed  by  a  digit)  will  appear  in  the  display.  For  a 
complete listing of error messages and their causes, refer to appendix A. 
To  clear  the Error display  and  restore  the  calculator  to  its  prior  condition, 
press any key. You can then resume normal operation. 
Overflow and Underflow 
Overflow. When the result of a calculation in any register is a number with 
a  magnitude greater than 9.999999999×1099, ± 9.999999999×1099 is placed 
in  the  affected  register  and  the overflow  flag, flag  9,  is  set.* Flag  9  causes 
the display to blink. When overflow occurs in a running program, execution 
continues until completion of the program, and then the display blinks. 
The  blinking  can  be  stopped  and  flag  9  cleared  by  pressing −, = or 
| 9. 
Underflow.  If  the  result  of  a  calculation  in  any  register  is  a  number  with  a 
magnitude  less  than  1.000000000×10-99,  that  number  will  be  replaced  by 
zero. Underflow does not have any other effect. 
 
                                                           * Recall that display does not include the last three digits of the mantissa.  
						

							62 Section 5: The Display and Continuous Memory 
 
Low-Power Indication 
When  a  flashing  asterisk,  which  indicates 
low  battery  power,  appears  in  the  lower 
left-hand  side  of  the  display,  there  is  no 
reason  to  panic.  You  still  have  plenty  of 
calculator  time  remaining:  at  least  10 
minutes  if  you  continuously  run  programs, 
and  at  least  an  hour  if  you  do calculations 
manually.  Refer  to  appendix  F  (page  259) 
for information on replacing the batteries. 
 
 
Continuous Memory 
Status 
The Continuous Memory feature of the HP-15C retains the following in the 
calculator, even when the display is turned off: 
 All numeric data stored in the calculator. 
 All programs stored in the calculator. 
 Position of the calculator in program memory. 
 Display mode and setting. 
 Trigonometric mode (Degrees, Radians, or Grads). 
 Any pending subroutine returns. 
 Flag settings (except flag 9, which clears when the display is 
manually turned off). 
 User mode setting. 
 Complex mode setting. 
When the HP-15C is turned on, it always ―wakes up‖ in Run mode. If the 
calculator is turned off, Continuous Memory will be preserved for a short 
period while the batteries are removed. Data and programs are preserved 
longer than other aspects of calculator status. Refer to appendix F for 
instructions on changing batteries. 
0.0000 *  
						

							 Section 5: The Display and Continuous Memory 63 
 
 
Resetting Continuous Memory 
If  at  any  time  you  want  to  reset  (entirely  clear)  the  HP-15C Continuous 
Memory: 
1. Turn the calculator off. 
2. Press and hold the = key, then press and hold the - 
key. 
3. Release the = key, then the - key. (This convention 
is represented as = / -.) 
When  Continuous  Memory  is  reset, Pr  Error (power  error) will  be 
displayed. Press any key to clear the display. 
Note: Continuous  Memory  can  inadvertently  be  interrupted  and 
reset if the calculator is dropped or otherwise traumatized. 
  
						

							 
 
 
 
 
Part ll 
HP-15C 
Programming  
						

							 
66 
Section 6 
Programming Basics 
The  next  five  sections  are  dedicated  to  explaining  aspects  of  programming 
the  HP-15C.  Each  of  these  programming  sections  will  first  discuss  basic 
techniques  (The  Mechanics),  then  give  examples  for  the  implementation  of 
these  techniques  (Examples),  and  lastly  discuss  finer  points  of  operation  in 
greater detail (Further Information). Read only as far as you need to support 
your use of the HP-15C. 
The Mechanics 
Creating a Program 
Programming the  HP-15C is  an easy  matter, based simply  on recording the 
keystroke  sequence  used  when  calculating  manually.  (This  is  called 
―keystroke  programming‖.)  To  create  a  program  out  of  a  series  of 
calculation steps requires two extra manipulations: deciding where and how 
to  enter  your  data;  and  loading  and  storing  the  program.  In  addition, 
programs can  be  instructed  to  make  decisions  and  perform  iterations 
through conditional and unconditional branching. 
As  we  step  through  the  fundamentals  of  programming,  well  rework  the 
falling object program illustrated in the Problem Solver (page 14). 
Loading a Program 
Program  Mode.  Press | ¥ (program/run)  to  set  the  calculator  to 
Program  mode (PRGM annunciator  on).  Functions  are  stored  and  not 
executed when keys are pressed in Program mode. 
Keystrokes Display  
| ¥ 000- Switches to Program mode; 
PRGM annunciator and line 
number (000) displayed.  
						

							 Section 6: Programming Basics 67 
 
Location  in  Program  Memory.  Program  memory – and  therefore  the 
calculators  position  in  program  memory – is  demarcated  by  line  numbers. 
Line  000  marks  the  beginning  of  program  memory  and  cannot  be  used  to 
store  an  instruction.  The  first  line  that  contains  an  instruction  is  line  001. 
Program  lines  other  than  000  do  not  exist  until  instructions  are  written  for 
them. 
You can start  a  program  at  any  existent  line  (designated nnn), but  it  is 
simplest  and  safest  to  start  an  independent  program  (as  opposed  to  a 
subroutine) at the beginning of program memory. As you write, any existing 
program lines will be preserved and ―bumped‖ down in program memory. 
Press t “ 000  (in  Program  or  Run  mode)  to  move to line  000 
without recording the t statement. In Run mode, ´ CLEAR M 
will also reset the calculator to line 000- without clearing program memory. 
Alternatively,  you  can  clear  program  memory,  which  will  erase  all 
programs  in  memory  and  position  you  to  line  000.  To  do  so,  press ´ 
CLEAR M in Program mode. 
Program  Begin.  A label instruction – ´b followed  by  a  letter 
(A through E)  or  number (0  through  9  or  .0  through  .9) – is  used  to 
define  the  beginning  of  a  program  or  routine.  The  use  of  labels allows  you 
to quickly select and run one particular program or routine out of several. 
Keystrokes Display  
´ CLEAR 
M 
000- Clears program memory and 
sets to line 000 (start of 
program memory). 
´ b A 001-42,21,11  
Recording  a  Program.  Any  key  pressed—operator  or  constant—will  be 
recorded in memory as a programmed instruction.* 
                                                           * Except the nonprogrammable functions, which are listed on page 80.  
						

							68 Section 6: Programming Basics 
 
 
Keystrokes Display  
2 002-         2   
* 003-        20  
9 004-         9 Given h in the X-register, 
lines 002 to 008 calculate . 005-        48 
8 006-         8 
. ÷ 007-        10 
¤ 008-        11 
Program End. There are three possible endings for a program: 
 | n (return) will end a program, return to line 000, and halt. 
 ¦ will stop a program without moving to line 000. 
 The end of program memory contains an automatic n. 
Keystrokes Display  
|n 009-     43 32 Optional if this is the last 
program in memory. 
Intermediate Program Stops 
Use ´ © (pause)  as a  program  instruction  to momentarily stop  a 
program and display an intermediate result. (Use more than one © for a 
longer pause.) 
Use  a ¦ (run/stop)  instruction to  stop  the  program  indefinitely.  The 
program  will  remain  positioned  at  that  line.  You  can  resume  program 
execution (from that line) by pressing ¦ during Run mode, that is, from 
the keyboard. 
Running a Program 
Run  Mode.  Switch  back  to  Run  mode  when  you  are  done  programming: 
| ¥. Program execution must take place in Run mode. 9 .8
2h  
						

							 Section 6: Programming Basics 69 
 
 
Keystrokes Display  
|¥  Run mode; no PRGM annunciator 
displayed. (The display will depend 
on any previous result.) 
The  position  in  program  memory  does  not  change  when  modes  are 
switched.  Should  the  calculator  be  shut  off,  it  always  ―wakes  up‖  in 
Run mode. 
Executing  a  Program. In Run  mode, press ´ letter  label or G digit 
(or  letter) label.  This  addresses  a  program  and  starts  its  execution.  The 
display will flash running. 
Keystrokes Display  
300.51 300.51 Key a value for h into the X-register. 
´A 7.8313 The result of executing program 
―A‖. (The number of seconds it 
takes an object dropped from 300.51 
meters high to hit the ground.F=
Restarting  a  Program. Press ¦ to  continue  execution  of  a  program 
that was stopped with a ¦ instruction. 
User  Mode.  User  mode  is  an  optional  condition  to  save  keystrokes  when 
executing letter-named programs. Pressing ´ U will  interchange  the 
´-shifted  and  primary  functions  of  the A through E keys.  You  can 
then  execute  a  program  using  just  one  keystroke  (skipping  the ´ or 
G). 
How to Enter Data 
Every program must take into account how and when data  will be supplied. 
This  can  be  done  in  Run  mode  before  running  the  program  or  during  an 
interruption in the program. 
1. Prior  entry.  If  a  variable  value  will  be  used  in  the  first  line  of  the 
program, enter it into the X-register before starting the program. If it 
will  be  used  later,  you  can  store  it  (with O)  into  a  storage 
register,  and  recall  it  (with  a  programmed l)  within  the 
program. 
  
						

							70 Section 6: Programming Basics 
 
This is the  method used above, where h was placed in the X-register 
before  running  the  program.  No v instruction  is  necessary 
because  program  execution  (here: ´A) both  terminates  digit 
entry  and  enables  the  stack  lift.  The  above  program  then  multiplied 
the contents of the X-register (h) by 2. 
The  presence  of  the  stack  even  makes  it  possible  to  load  more  than 
one  variable  prior  to  running  a  program.  Keeping  in  mind  how  the 
stack  moves  with  subsequent  calculations  and how  the  stack  can  be 
manipulated (as with ®), it is possible to write a program to use 
variables which have been keyed into the X-, Y-, Z-, and T-registers. 
2. Direct  entry.  Enter  the  data  as  needed  as  the  program  runs.  Write a 
¦ (run/stop) instruction into  the  program  where  needed  so  the 
program  will  stop  execution.  Enter  your  data,  then  press ¦ to 
restart the program. 
Do  not  key  variable  data  into  the  program  itself.  Any  values  that  will  vary 
should be entered anew with each program execution. 
Program Memory 
At  power-up  (Continuous  Memory  reset),  the  HP-15C  offers  322  bytes  of 
program  memory  and  21  storage  registers. Most program  steps 
(instructions)  use  one  byte,  but  some  use  two.  The  distribution  of  memory 
capacity  can  be  altered,  as  explained  in  appendix  C.  The  maximum 
attainable  program  memory  is  448  bytes  (with  the  permanent  storage 
registers—RI,  R0,  and R1 — remaining);  maximum  number  of  storage 
registers is 67 (with no program memory). 
Example. Mothers  Kitchen,  a  canning 
company,  wants  to  package  a  ready-to-
eat  spaghetti  mix  containing  three 
different  cylindrical  cans:  one  of 
spaghetti  sauce,  one  of  grated  cheese, 
and  one  of  meatballs.  Mothers  needs  to 
calculate  the  base  areas,  total  surface 
areas, and volumes of the three different 
cans.  It  would  also  like  to  know,  per 
package,  the  total  base  area,  surface 
area, and volume.