HP -28S Manual page 185

The Current Directory. Initially, the only directory that exists is the
built-in directory HOME. After creating other directories, you can
choose which is the current directory-that is, which set of variables
appears in the USER menu.
To choose the current directory you evaluate its name-for example,
if you've just created a directory, you make it the current directory by
pressing the appropriate key in the USER menu.
Almost all commands that use variables work only in the current di-
rectory, since the purpose of multiple directories is to control which
variables are available. You can alter a variable only if it's in the cur-
rent directory.
The following commands in the MEMORY menu act on the current
directory.
Command Description
VARS Returns a list of names of all variables and directories in
the current directory.
ORDER
CLUSR
Reorders variables and directories in the current direc-
tory as specified by a list.
Purges all variables and empty directories in the current
directory.
The Current Path. You can check where you are in the directory
structure by executing the command PATH. It returns a list specifying
the sequence of directories from the HOME directory to the current
directory.
In some cases the calculator searches not only the current directory,
but the entire current path. The search begins in the current directory;
if the variable isn't found, the search continues in the parent direc-
tory; and this process continues back to the HOME directory.
This occurs in the evaluation of names-after all, you could never re-
turn to a parent directory if you couldn't successfully evaluate its
name. Evaluation of names occurs when you key in an unquoted
name, when you plot or use the Solver, when you evaluate algebraics
on the stack, and so on.
184 20: Memory