HP 33s - Manual (Page 192)

13–8 Programming Techniques
Example:
The "Normal and Inverse–Normal Distributions" program in chapter 16 uses the
x
<y? conditional in routine T:
Program Lines:
(In RPN mode)
Description
.
.
.
!
ª Calculates the correction for X
guess
.
!

! - % Adds the correction to yield a new X
guess
.
!
 
!

)

!
 º
<¸@ Tests to see if the correction is significant.
!
 ! ! Goes back to start of loop if correction is significant.
Continues if correction is not significant.
!
  %
!
 #$ % Displays the calculated value of X.
.
.
.
Line T0009 calculates the correction for X
guess
. Line T0013 compares the absolute
value of the calculated correction with 0.0001. If the value is less than 0.0001
("Do If True"), the program executes line T0014; if the value is equal to or greater
than 0.0001, the program skips to line T0015.
Flags
A flag is an indicator of status. It is either set (true) or clear (false). Testing a flag is
another conditional test that follows the "Do if true" rule: program execution
proceeds directly if the tested flag is set, and skips one line if the flag is clear.
Meanings of Flags
The HP 33s has 12 flags, numbered 0 through 11. All flags can be set, cleared,
and tested from the keyboard or by a program instruction. The default state of all
12 flags is clear. The three–key memory clearing operation described in appendix
B clears all flags. Flags are not affected by
{ c {} {&}.