Miscellanous Information about k7                   Jim Overbeck, January 1997

	1. What is k7?   k7 is a high precision calculator program that uses
text input (rather than using a mouse to press keys on a simulated hand
calculator).  It evaluates algrebraic expressions and has a crude "programming"
capability.  Its precision is variable up to 270 binary bits and 60 decimal digits,
beyond the capability of a 80X87 floating point processor.  k7 comes in two
versions: a non-Windows version which has its own fixed size windows, and a Windows
3.1 and 95 version.  A complete technical manual may be accessed by clicking "Help"
in the Windows version or typing "help" in the non-Windows version.  k7 runs on
IBM-compatibles with 80386, 80486, or Pentium processors. The non-Windows version
probably also runs on an 80286 or 80186, but this has not been verified. 

	2. What motivated k7?  
	A. Practical engineering calculations that require accurate subtraction of 
numbers which are very nearly equal.  The primary calculations were the optimization
of diffraction limited lens designs and the optimization of very accurate control
systems.
	B. Desire for a test bed for a few new software paradigms. The paradigms
include:
	automatic assignment of 2-lettter variable names to numbers
	automatic re-use of these variable names if a variable name is never
		referred to
	simultaneous, nearly transparent calculations in base 2 and base 10
	flexible algorithms for algrebraic expression parsing, depending upon
		user's preferences

	3. What are some limitations of k7?
	A. On-line editing of previously entered lines of text is not available.
However k7 dumps its contents into a file which may be edited off-line by any
ASCII text editor.  The contents of this file may then be read later by k7.
	B. k7 lacks array variables, names of variables outside a prescribed range,
and named entry points.  Entry points are identified by sequentially assigned line 
numbers, as in Fortran or Basic, only worse.
	C. k7 lacks branching instructions and logical operations.
	D. k7 lacks local variables within subroutines. All variables are global.
	E. k7 lacks looping capability.  The only instructions provided for doing
repeated calculations are "call" (followed by a line number) and "return".

	4. Is there a tutorial on how to use k7?  Yes and no.  Such a tutorial was
written and included in a printed manual.  Its use of screen images prevented it
from being converted to machine readable form for inclusion on this disk.  If there
is enough demand I will make more copies and distribute them by mail for just 
enough money to cover copying and postage.  Write to k7 Associates, P.O. Box 91,
Hingham, MA 02043.
	But here is an attempt at a tutorial.  Say we want to calculate 
	sqrt(1 + (3.5/(50*sqrt(2/ln(2))))**2).    **2 means squared in Fortran.
You may be used to ^2 in other languages. k7 uses the Fortran convention. There
are many ways to calculate this. Use the one which is most comfortable for you.
	A. Type the expression given above, but replace the period after **2)
with a depression of the "Enter" key on your keyboard.
	B. Do the calcuation in pieces, assigning names, aw, ap, and ar to
intermediate results. In the following, the line numbers 0> through 4> are typed
by k7 and the rest is typed by you:
	0> aw = sqrt(2/ln(2))
	1> ap = 3.5
	2> ar = ap/aw
	3> sqrt(1 + (ar/50)**2)
	4>
	C. Imagine that for some or all of the steps you are using a HP Reverse
Polish calculator. Do not bother to add closing parentheses if they are not really
necessary. Type:
	0> sqrt(2/ln(2
	1> ap = 3.5
	2> b/
	3> 50/
	4> **2
	5> 1+
	6> sqrt
	7>
Note that on line 3 the letter b comes from the fact that one sees (when looking at
the screen) that k7 automatically assigned the letter b to the result of the
calculation on line 0. Similarly it assigned the letter a to the number 2.
Note that lines 0 and 1 do not use Reverse Polish, but line 2 through 6 do. Line 0
could instead have been
	0> 2
	1> 2
	2> ln
	3> /
	4> sqrt
 
	5. Are components of k7 available in a form so that they may be called as
subroutines from another program?  Also yes and no.  This repackaging of k7 was
about 90% complete in 1992 when it was pushed aside by a higher priority project.
But the subroutine version had some nice features. The primary one was switching
between high speed, lower precision (80X87) calculations and the lower speed, 
higher precision calculation provided by the k7 modules.  This was necessary since
the target of k7, optimization, requires all the computing speed one can get.
Precision beyond that of the 80X87 is only needed at certain critical times,
typically when the optimization process is near a local minimum of a cost function.

	6. How do I install k7?    k7 was written before automated installation
and unzipping of files was common.  So you do not perform a "modern" operation like
running a program named "install.exe."  Instead you just copy files.  This was
very foolproof when there was only the one non-Windows version of k7.  Now, with
two versions, it is customary, but not necessary, to keep the two versions in
separate directories (or separate folders, in current jargon.)  On the distribution
disk the non-Windows files are in the directory named k7nonwin and the Windows files
are in the directory named k7window.  The names of the non-Windows files start with
k7 and the names of the Windows files start with k7w.

	7. The on-line help function in k7 is not what I am used to. What gives?
The on-line help function for the Windows version is not "Windows Help." You may
click on any line in the index in order to go to the chapter indicated by that
line.  But these lines are displayed in black, not green.  There are no key words
such as one normally sees in green when using "Windows Help."

	8. The non-Windows version is writing files to disk without my asking it
to do so. What gives?  Long ago this was not considered to be proper, since one
might be running a program which resided on a floppy.  If you want to disable the
writing of files, type "help" to get to the "Status" screen. Then type 1 to get
to the list of help topics. Then 15 to get to its second page. Then 3 to learn
more about this.  OR: Type "panel" to get to the first control panel screen. Then
the letter "a" to get to the second control panel screen. Then the letter "a"
again to get to the third control panel screen. Then letter "a" again to get to
the fourth such screen. Now combinations of spacebar and tab will enable you to
turn logging to disk on or off.  Sorry about that.  The default setting for the
Windows version is to not write files to disk.  You may change this by clicking
the "Write Logs" entry in the "File" pulldown menu.

	9. How do I exit the non-Windows version of k7?  Type either "quit" or
"exit".  I don't know why one would want to use the non-Windows version if
you have a computer that is running Windows.

	10. On what versions of Windows will the Windows version of k7 run?  It
runs fine on 3.1 and two versions of 95.  It should also run fine on NT.  There
are occasional crashes on 3.0, but I am convinced these are the fault of 3.0,
not k7.

	11. Given the extreme limitations in paragraph 3 above, is there any way
to do a really complex calculation?  Try writing the calculation in a text file,
using an ASCII text editor, and using the "Read" option in the "File" pulldown
menu (in the Windows version.)  Or type "read" followed by a file name in the
non-Windows version.  Sorry, but there is no guarantee that this "safety valve"
will provide you with the power you need.  It certainly will not provide you
with array variables, or logical operations, for example.  The only sensible way
to increase the power of k7, I think, is to have its modules be callable from C
or C++ programs.