HP 15c Manual

 Section 14: Numerical Integration 201 
 
Because  the  accuracy  of  any  integral  is  limited  by  the accuracy  of  the 
function (as  indicated in the  display  format), the  calculator  cannot compute 
the  value  of  an  integral  exactly,  but  rather  only approximates it.  The 
HP-15C  places  the  uncertainty* of  an  integrals  approximation  in  the  Y-
register  at  the  same time  it  places  the  approximation  in  the  X-register.  To 
determine  the  accuracy  of  an  approximation,...

202 Section 14: Numerical Integration 
 
If  the  uncertainty  of  an  approximation  is  larger  than  what  you  choose  to 
tolerate,  you can decrease  it by  specifying a  greater  number of digits in  the 
display format and repeating the approximation.* 
Whenever  you  want  to  repeat  an  approximation,  you  dont  need  to  key  the 
limits  of  integration  back  into  the  X- and  Y-registers.  After  an  integral  is 
calculated,  not  only  are  the  approximation  and  its  uncertainty...

 Section 14: Numerical Integration 203 
 
In  the  preceding  example,  the  uncertainty  indicated  that  the  approximation 
might be  correct  to  only  four  decimal  places.  If  we  temporarily  display  all 
10 digits of the  approximation, however, and compare  it to the  actual  value 
of  the  integral  (actually,  an  approximation  known  to  be  accurate  to  a 
sufficient  number  of  decimal  places),  we  find  that  the  approximation  is 
actually more accurate than its uncertainty...

204 Section 14: Numerical Integration 
 
Memory Requirements 
f requires  23  registers  to  operate.  (Appendix  C  explains  how  they  are 
automatically  allocated  from  memory.)  If  23  unoccupied  registers  are  not 
available, f will not run and Error 10 will be displayed. 
A  routine  that  combines f and _ also  requires  23  registers  of 
space. 
For Further Information 
This  section  has  given  you  the  information  you  need  to  use f with 
confidence  over  a  wide  range  of...

 
205 
Appendix A 
Error Conditions 
If you attempt a calculation containing an improper operation – say division 
by  zero – the  display  will  show Error and  a  number.  To  clear  an  error 
message, press any one key. This also restores the display prior to the Error 
display. 
The  HP-15C  has  the  following  error  messages.  (The  description  of Error 2 
includes a list of statistical formulas used.) 
Error 0:  Improper Mathematics Operation 
Illegal argument to math routine: 
÷, where x = 0....

206 Appendix A: Error Conditions 
 
 x or y is noninteger; 
 x < 0 or y < 0; 
 x > y; 
 x or y ≥ 1010. 
Error 1:  Improper Matrix Operation 
Applying  an  operation  other  than  a  matrix  operation to  a  matrix,  that  is, 
attempting  a  nonmatrix  operation  while  a  matrix  is  in  the  relevant  register 
(whether the X- or Y-register or a storage register). 
Error 2:  Improper Statistics Operation  
’ n = 0 
S n ≤ 1 
j n ≤ 1 
L n ≤ 1 
Error 2 is also displayed if division by zero or the...

 Appendix A: Error Conditions 207 
 
Error 3:  Improper Register Number or Matrix Element 
Storage  register  named  is  nonexistent  or  matrix  element  indicated  is 
nonexistent. 
Error 4:  Improper Line Number or Label Call 
Line  number  called  for is currently  unoccupied  or  nonexistent  (>448);  or 
you  have  attempted  to  load  a  program  line  without  available  space;  or  the 
label  called  does  not  exist;  or User  mode  is  on  and  you  did  not  press ´ 
before ¤, , @, y or ∕....

208 Appendix A: Error Conditions 
 
+ or -, where the dimensions are incompatible. 
*, where: 
 the dimensions are incompatible; or 
 the result is one of the arguments. 
∕, where the matrix is not square. 
scalar/matrix ÷, where the matrix is not square. 
÷, where: 
 the matrix in the X-register is not square; 
 the dimensions are incompatible; or 
 the result is the matrix in the X-register. 
> 2, where the input is a scalar; or the number of rows is odd. 
> 3, where the input is a scalar; or the...

 
209 
Appendix B 
Stack Lift and 
the LAST X Register 
The  HP-15C  calculator  has  been  designed  to  operate  in  a  natural  manner. 
As you  have  seen  working  through this  handbook,  most calculations do not 
require you to think about the operation of the automatic memory stack. 
There are occasions, however – especially as you delve into programming – 
when  you  need  to  know  the  effect  of  a  particular  operation  upon  the  stack. 
The following explanation should help you. 
Digit...

210 Appendix B: Stack Lift and the LAST X Register 
 
Disabling Operations 
Stack  Lift. There  are  four  stack-disabling  operations  on  the  calculator.* 
These  operations  disable  the  stack  lift,  so  that  a  number  keyed  in  after  one 
of  these  disabling  operations  writes  over  the  current  number  in  the 
displayed  X-register  and  the  stack  does  not  lift.  These  special  disabling 
operations are: 
v    `    z    w 
Imaginary  X-Register. A  zero  is  placed  in  the...