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To: I1002812--IBMMAIL NFB R&D Committee
FROM: Steve Jacobson - IT Order Proc. Mktg. and Dist.
3M Company - 555-01-03 Phone: (612) 733-9780
St. Paul, MN 55144 FAX: (612) 736-6037
Subject: Scientific Calculator
The discussion of the scientific calculator is most interesting. Whether
we use ALT keys or not to generate certain operations, I would think
that we will have to assign ASCII codes to every operation if we expect
to run programs from files. We may wish therefore to choose ASCII codes
that can be easily generated by keystrokes on other systems. This means
that we would probably not wish to use the upper 128 extended ASCII
codes.
However, for a calculator to be truly useful, we must pay some attention
to the layout of the commands that we use. For example, someone using
our calculator a great deal will probably enter information using the
numeric pad rather than the top row of numbers. This would place ALT-5
and CONTROL-H well out of reach. We may still, therefore, need to use
some special key combinations on IBM compatibles to make data entry
efficient, even if these keys indirectly generate ASCII codes.
Also, we will likely want to edit formulas that have been entered using
the arrow keys. These keys are also, in and of themselves, not standard
keys in that they don't directly generate ASCII characters. Again,
though, we could support ASCII cursor movement characters in addition to
the arrow keys. Some editors, for example, support the Word-star cursor
movement keys which generally consist of pressing the letters under the
left hand along with the control key. If we support program files,
though, cursor movement keys can be kept to a minimum since complex
editing tasks can be done with a standard editor.
To touch upon a question raised earlier by Dr. Nemeth, most languages
with which I am familiar return non-ASCII keystrokes as two-byte codes.
The first code is usually a null, while the second is an extended key
code. Because these codes are two bytes, they may only be decoded using
single character functions. The extended key code is usually the scan
code of the physical keystroke, but some keys such as the
CONTROL-LEFT-ARROW and CONTROL-RIGHT-ARROW have different extended key
codes than their left and right arrow counterparts. This eliminates the
need for the programmer to check the status of the control key. These
extended key codes are listed in an appendix in the back of the IBM
BASIC manual among other places.
As usual, most of us will have more ideas to complicate the project
rather than make it simpler, but from my experience with the Type 'n
Speak, I believe key layout is important on a calculator using the full
keyboard.
Regards,
Steve Jacobson
IBMMAIL: USMMMXBL
INTERNET: USMMMXBL@IBMMAIL.COM
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