From: billw@hpcvra.CV.HP.COM (William C Wickes)
Date: Mon, 12 Mar 1990
Subject: HP 48SX Vectored Enter
Organization: Hewlett-Packard Co., Corvallis, OR, USA
Newsgroups: comp.sys.handhelds

[Note: The following article by the head of the HP 48 design team
 was posted a mere six days after the HP 48 was formally introduced.
 2.3354366 years later, here it is, better late than never...   -jkh-]

The HP 48SX manuals do not document a very powerful feature that we
call "Vectored ENTER," that allows you in effect to redefine or bypass
the command line parser and to have a shot at the stack etc. after the
command line has been executed.

Keys that execute an automatic ENTER perform a two-step process:

1.  The command line is parsed and evaluated.
2.  The key definition is executed.

When flags -62 and -63 are both set, the system extends this process
as follows:

1.  The current path is searched for a global variable named àENTER
(here "à" is the Greek alpha character--character 140).  If present,
the command line is entered as a string object and àENTER is
executed.  If absent, the command line is parsed and evaluated
normally.

2.  The key definition is executed.

3.  The current path is searched for a global variable named áENTER
("á" is Greek beta--character 223). If present, then a string
representing the key definition is put on the stack, and áENTER is
executed.  The string is the key definition object's name if it is a
command, XLIB name, global or local name, or an empty string for other
object types; its primary purpose is to implement things like the
TRACE mode on other calcs, where you can print a running record of
what you do.

A simple example of the use of àENTER is to create a more convenient
binary calculator, where àENTER slaps a "#" on the front of the
command line so you don't have to bother when entering numbers.