HP HP-28S - Page 260

• Local-variable structure. PRESERVE creates a local variable just to
remove
the object from the stack briefly; its defining program does
little except evaluate
the program argument on the stack.
Program
F.:CLF
.;. f
E'·}RL
f ::nclF
::;:.
I ENTER I
c::J PRESERVE I STO I
Comments
Begin the program.
Recall a 64-bit binary integer
representing the status of all 64
user flags.
Store
the binary integer in a local
variable
f.
Begin the defining program.
Execute
the program argument.
Restore the status of all 64 user
flags.
End
the defining program.
End
the program.
Put the program on the stack.
Store
the program as PRESERVE.
Example. PRESERVE is demonstrated in the program BDISP.
BDISP (Binary Display)
Display a number in HEX, DEC, OCT, and BIN bases.
Arguments
Results
1 : #
n
1 : #
n
1 : n
1 :
n
Techniques:
• IFERR .. , THEN ... END (error trap). To accomodate real numbers,
BDISP includes the command F.:.;. 8 (real-fa-binary). However, this
command causes an error if the argument is already a binary
integer.
28: Programming Examples 259