HP HP-28S - The Command Line

The Operation Index in the back of the Reference Manual identifies
each built-in procedure as an operation, a command, a function, or an
analytic function. As a rough guide, here are general comments about
each type.
• Most
non-programmable operations can be executed only by press-
ing a key. However, there are programmable equivalents for some
operations: for example, the I TRIG I operation (to select the TRIG
menu) can be effected in a program by executing 21 MEt·W, and
the RAD operation (to select Radians angle mode) can be effected
by executing 60 FS.
• Most RPN commands involve manipulating the stack or altering
user memory rather than calculating mathematical values.
• Most
non-analytic functions are mathematical calculations without
inverses-that is, they return some characteristic of the arguments,
but the arguments can't be reconstructed from the result. Examples
include integer part and fractional part, absolute value and sign.
• In
mathematics, a function of complex variables is analytic if it can
be expressed as a power series at every point in its domain; in this
case
it has an inverse and a derivative. The HP-28S makes a few
exceptions to this definition. For example, no derivative is given for
the command :~, although one would be possible; a derivative is
given for the function ASS, although the function is non-analytic at
the point 0 + Oi.
Every built-in procedure is available on a key, either on the keyboard
or in a menu. When you press a key, the exact result depends on the
type of procedure and the entry mode, as discussed in the next
chapter.
17: Operations, Commands, and Functions 165
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