Cas Settings; Selecting Cas Settings; The Cas Directory, Casdir - HP 48gII Advanced User's Reference Manual

Input: The input argument or arguments that the operation needs. If the operation uses more than
one input argument, details of the arguments and the order in which to supply them are
provided: in argument order for algebraic mode and in stack order for RPN mode.
Output: The output that the operation produces.
In RPN mode, the outputs are placed on the stack.
•
In algebraic mode, the outputs are displayed; if there is more than one output, they are
•
written to a list.
As with the input arguments, the outputs for both algebraic and RPN mode are described.
Flags: Details of how flag settings affect the operation of the function or command. See also the
section below on CAS Settings.
Example: An example of the function or command. Examples are also available in the built-in CAS help
on the calculator. The examples given here are shown in Algebraic mode, but can be
transferred to RPN mode according to the descriptions given in "Input" and "Output".
See also: Related functions or commands.

CAS Settings

Selecting CAS Settings

CAS settings are selected using the CAS MODES input form, described in Chapter 1 of the User's Manual.
Selecting a mode is equivalent to setting or clearing one of the system flags, the flag numbers are given in the
"Flags" part of the operation descriptions.
Pressing the L key in the CAS MODES input form displays a menu that allows the user to calculate settings.
For example, if the Modulo field is selected in the CAS MODES form, and L is pressed, the following menu
keys are available.
!TYPES lists the types of object that can be chosen for this setting. For the modulo, this can be a real number or
an integer. For checked mode settings, this can only be a real number; if it is zero the mode is unchecked, if it
is anything else the mode is checked.
!CALC lets the user calculate a value for the setting, for example a new value for the modulo setting can be
calculated. The !STS! menu key allows the user to switch the heading lines between the "CAS MODES" heading
and the normal heading lines, so that the user can see what the current settings are while carrying out a
calculation.
!RESET allows the setting to be reset to its default value, or all CAS settings to be reset to their default values.
See Appendix C in the User's Guide for further details of the CAS settings, and for other information about
the CAS. Information on the Help system of the CAS is provided in Appendix C and also in Appendix H of
the User's Guide.

The CAS directory, CASDIR

CAS settings are stored as flag settings, and as variables in the CASDIR directory, which is automatically
created as a subdirectory of the HOME directory. Variables in this directory include:
VX: A name or list of names of the current CAS variable or variables. Default value is X
MODULO: The current modulus used for CAS modulo operations. Default value is 13, but is reset to 3
by the !RESET key in the CAS menu.
PERIOD: The period for CAS periodic operations, 2π by default.
EPS: The value chosen such that coefficients in a polynomial smaller than this value are replaced
with 0 by the EPSX0 command. 1E-10 by default.
REALASSUME: A list of the names of variables that some CAS operations treat as real numbers when
complex mode is set. If additional assumptions are made on any variables, these are
included here. By default the list is {X, Y, t, S1, S2}.
4-2 Computer Algebra Commands