HP 48G - Page 32

The grob commands (under (i) perform a wide
variety of manipulations on any given grob (graphics
object). Notes: The two LCD commands let you eas-
ily save and recall screen displays. And the ANIFATE
command allows you to define a set of fixed grobs,
then cycle the display through them quickly enough to
achieve the effects of animation.
The PICT commands (under [II&M) perform a wide
variety of manipulations on the grob currently stored
inthe reserved namePICT. Notes: Keep in mind that
you can specify the pixels in a grob either in pixel
coordinates, via a list of binary integers, 1. #horizontal
#vertical I; orin user-defined coordinates, via a com-
plex number, {x y). The scale of the user-defined
units depends on the current settings stored in PPAR.
There are also handy commands for quickly drawing
lines, boxes and arcs.
The input commands (under [lIZIM) give you ways
to let a user input values during program execution.
Notes: You can use PROMPT or INPUT to cause a
program to halt with a message asking for user re-
sponse; or you can use WAIT or KEY to detect or
identify user keystrokes; or you can use CHOOSE to
build a “fiTE-box” for the user to select from; or the
INFORM command lets you build an input screen—
similar to those of the built-in applications.
The outputcommands (under [IiITERl) give you ways
to format program output. Notes: You can sound the
tone generator with BEEP; or your can use MSGEOX to
convey intermediate messages during program ex-
ecution; or you can use FREEZE or DISF to halt pro-
gram execution to allow a user to inspect output.
The run control commands (under [TH) let you
troubleshoot a program: With the name of the desired
program as the stack argument, you execute [{HTE,
which initiates execution but then halts immediately.
Thereafter, you can single-step (IEELIB) through the
execution to examine the effect of each program step
(or shows every subroutine step as well); or
lets you look a couple of step ahead without
executing those steps.
The error commands (under FTAIR) offer ways to
detect and recover from run-time errors. The IFERE-
THEM-ELSE construct lets you execute a command
tentatively—you can undo it if it causes an error.
30 THe HP 48G/GX Pocker GuiDe