(I'm not sure I have this 100% right, but here it goes):

First Graphing Calculator: Casio 7000G in 1985

First Foldable/Clamshell Calculator: HP 28S. There is one on the market today, Casio fx-9860 Slim.

First one with Natural Input: HP 48S

First one with a Stylus: Casio Classpad 300

First one with a Touchpad: TI nSpire Touchpad

First one with "documents": I want to say the HP 38G/39G; I think that was slightly before Casio came out with their e-activity.

First one with external backup: HP 48S

First one I ever owned: TI 81 back in 1991 - I was in high school. The first HP graphing calculator I owned was the HP 48G in 2000. The first Casio graphing calculator I owned was the fx-Algebra 2 (I think it was 2004).

The 28C was released one year(?) before the 28S.

First one with external backup? You need to go *way* back - check out the CompuCorp 3xx series. Though a lot larger than the 48, I'd still call them a "pocket calculator".

If you consider them being too large, the 41 or Sharp PC-series from about the same time offer external backup as well.

The first calculator I owned was the fx-7000G (199 German Marks back then), soon to be replaced by a 28C (444 German Marks).

Your are right on several points:

* HP28C was out nearly one year sooner than HP28S, but due to distribution and logistic facts, HP28S apears only a few months or weeks after the HP28C in many dealer shops ! (Especialy in Europe)

* Right in 1982 I own a SHARP PC-1211 with CE-121 Cassette Interface which I use for external backups on audio tapes. Note that 28 years later, most of these backups are still available and functional.

You should add the first graphing calculator with a color display.

The first foldable/clamshell calculator dates *way* back too (how could I forget - I have a massive sterling silver encased one <g>):

http://www.vintagecalculators.com/html/facit_1106_sharp_el-805s.html#EL-8009

I'm unsure about the "Natural Input" - I'd say the (earlier) Casio BASIC-capable models offered the same feature. AFAIR you were able to enter something like "sqr(sin(45)+cos(45))="...

How could I forget again (since I own both of them, maybe I'm getting old): the first stylus-based calculators are without doubt the Litton Royal II and III:

http://www.vintagecalculators.com/html/royal_digital_iii___iv.html

Thanks Palmer, I did forget:

Color Graphing: Casio 9850g Series (late 1990s, early 2000s)

In addition: the one with backlight (that I know of) Casio 9860g Series (GII, Slim)

First one with a Matrix/List Editor: HP 48S

First with 3D Graphing as a feature: TI-89 (?) I am truly not sure about this one.

The Royal Digital III looks like a Price Is Right display. Four digits-display? Wow. They are neat looking calculators, thanks Frank.

The TI 92 predates the 89. It runs the same software (at least in the "plus" version. Don't know about the plain 92's graphics capabilities.

You could add the first with full alpha keyboard (28C or TI-92? No: Sharp PC-1210 or Casio FX702P is more probable.)

*Edited: 11 Mar 2010, 11:53 a.m. *

The first color graphing calculator was the CFX-9800G from early 1990s.

I'am not sure, but probably the FX-7500G was the first foldable graphing calculator.

Try this one - with only 3 digits:

Sharp EL-120

I think this is about the oddest calculator ever inventend. Please note the special "+1" counter button (below the display).

Btw: they (oddly enough) even made an OEM version for Quelle, Germany (formerly the largest mail order in Europe, maybe worldwide).

While the EL-120 displays three digits at a time it can calculate and display many more. For example, in the reference that you give when 123456789 is entered the user can see three digits at a time, i.e., 123 then 456 and then 789 where the actual displays are

+123,,

456 ,

789.

and the machine does more than in the discussion in the reference. For example, with the A M switch in the A (automatic) position the result of a calculation will be automatically sequenced through the display with a pause of about one second for each part of the answer.

The machine can actually calculate up to twelve digits, nine to the left of the decimal point and three to the right of the decimal point. For example, if you multiply 111111.1 times 1111.11 the machine will display

+123,,

456 ,

645.

.321