Memory is used for a variety of purposes in the HP-28S, including
the command line, the stack, user memory, recovery features, and the
operating system. The command line and the stack are described in
chapters 18 and 19. This chapter primarily discusses user memory,
including directories; it also discusses low-memory conditions and its
effects on recovery features and the operating system.
User memory can contain variables, and it can contain directories to
organize the variables.
A variable is the combination of a name object and any other object.
The name object represents the name of the variable; the other object
is the value or contents of the variable.
Global variables are those that are stored in user memory. There are
also local variables, which are created by program structures and exist
only during execution of the program structures. Local variables are
primarily a substitute for stack manipulations and are described in
chapter 19, "The Stack." In the present chapter, the term "variables"
indicates global variables.
The contents of a variable can be any type of object. In part 1 you
created numerical variables, program variables, algebraic variables, list
variables, and array variables. You even created name variables,
where the contents of the variable was the name of another variable.