Model  High Contrast Screen  Colors  Memory  Symbolic Algebra  Finance & Advanced Stats  Program Library  Autodim  Year 
fxCG10/fxCG20  384x216 pixels  65000  64k+16Mb Flash  N  Y  N  Y  2011 
9860GII / 
Y  B/W  64k+1.5Mb Flash  N  Y  N  Y  2009 
9860G Slim  Y  B/W  64k+1.5Mb Flash  N  Y  N  Y  2007 
9860G / 
Y  B/W  64k+1.5Mb Flash  N  Y  N  Y  2005 
9860G AU  Y  B/W  64k+800k Flash  N  Y  N  Y  2005 
9750GII  Y  B/W  64k  N  Y  N  Y  2009 
7400GII  Y  B/W  20k  N  N  N  Y  2009 
9750GA PLUS  Y  B/W  32k  N  Y  N  Y  2008 
9750G PLUS  N  B/W  32k  N  Y  N  Y  2002 
9750G  N  B/W  32k  N  N  N  N  1997 
9850GC PLUS / (White) 
N  5  64k  N  Y  N  Y  2004 
9850GB PLUS  N  5  32k  N  Y  Y  Y  BE=1998, WE=2002 
9850Ga PLUS / (Black) 
N  5  32k  N  Y  N  Y  1997 
9850G  N  5  32k  N  N  N  N  1996 
9950GB PLUS  N  5  64k  N  Y  Y  Y  BE=1998, WE=2002 
9950G  N  5  64k  N  N  N  N  1996 
9970G  N  5  64k  Y  Y  N  Y  1998 
Algebra FX 2.0 PLUS 
N  B/W  144k +768k flash  Y  Y  N  Y  2001 
Algebra FX 2.0 
N  B/W  144k +768k flash  Y  N  N  Y  1999 
FX 1.0 PLUS  N  B/W  144k +768k flash  N  Y  N  Y  2002 
FX 1.0  N  B/W  144k +768k flash  N  N  N  Y  2000 
7400G PLUS  N  B/W  20k  N  N  N  N  1999, GY=2004 
7450G  N  B/W  20k  N  N  N  N  1999 
7400G  N  B/W  7k  N  N  N  N  1996 
These models use an updated BASIC programming language which is partly
compatible with the 1st generation except that array variables which were
removed in favour of using lists and matrices instead and the names of some commands
were changed. New commands included For Next Loops, If then Else commands, DoWhile,
PixelOn, PixelOff, Getkey to detect input and Locate  to place text anywhere
on screen. Statistics data is stored using the lists facility.
The screen dimensions of these models are: (except the 7400s, 9860s and 9750GA PLUS)
The 9860 series, the 9750GA PLUS and the 9750GII have a slightly larger high contrast screen but the same number of pixels.
The 7400 has:

The 9860 has a USB port, natural display input, spreadsheet and a faster CPU than previous models.
It has a function catalog which has a better userinterface than the Algebra FX catalog.
It can use complex numbers with log, ln, e^, 10^, sqrt, and ^ but not with trig functions.
It can store complex numbers in lists, but not in matrices.
There is an official 9860 emulator and a software development kit (SDK) for writing c programs.
It has a new highcontrast black and white screen which is much clearer than the blueishgreenish grey
screens on older models.
The 9860G Slim is a foldup pocket version. Its screen has a backlight. It has inbuilt syntaxhelp for each function. 
From the 9750s add colour to get the 9850s, add 64k memory to get the 9950s and add symbolic algebra to get the 9970s. The PLUS models added TVM financial functions, and stats distributions and tests and anova: Normal, t, Chi, F, Binomial, Poisson. The GB+ models added a program library but this was absent in the 9850GC+. The 9850GC+ also had 64k. The 7400G series and the first 9750G,9850G,9950G models don't havedimensionsetup from within programs, that the PLUS and other models have. 
The FX 1.0/Algebra FX 2.0 range are commonly abbreviated to afx compared to cfx for the 9850 range.
The afx runs basic programs slower than the 9850 range, and use an awkward menu system. Also the flash memory has a very short lifespan, resulting in broken calculators after a few years, whereas models like the 7000G are still working after more than 20 years. The afx can store complex numbers in lists and matrices, and use use complex numbers with functions. e.g. sin(1+i). The '=>' cannot be typed symbol on the afx although it can be transferred from a pc to the calc with FA123. Advanced stats and other features can be added to these models using their flash memory. The Algebra FX 2.0 PLUS has other features extra to the Algebra FX 2.0. See Casio's website Software for transferring assembly,c and pascal programs to the afx has been developed by the online community. For details see:http://www.casioworld.fr.st/ 
The 7400 series lack some of the more advanced 9850 features such as the Getkey and Locate commands,
integration, summation, complex numbers, hyperbolic functions, base n, logic and/or/not,
engineering notation, matrices, polar graphs and function memory.
However they do have fraction functions: Simp,Int/ and Rmdr which are not present on the more advanced models. The 7450G and 7400G PLUS have a communication port and the commands PlotOn, PlotOff, PlotChg and FLine.
The 7400G PLUS (GY) is the same as the 7400G PLUS but with a new streamlined snapon case design. 
More compatibility issues are discussed in this forum thread. 
c.1985
Originals 
c.1990
Power Graphic 
c.1993
Icon Menu Power Graphic 
c.1993
Icon Menu Power Graphic 24k Models 
fx6000G (half screen), fx7000G, GA, GB, 7200G
(422) fx7500G(wallet form)
fx8000G (printer)
fx8500G (printer)

fx7700G, GB, Gbus
(4228) fx8700G
fx8700GB

fx7700GE, GH
(4000) 
fx9700GE
(24000) cfx9800G

Also produced in 1991 was the fx6300G (400 bytes) which didn't swap display modes with G<>T function. Instead a small corner of the screen is used for graphing.
In 1995 there was the fx7300G (500 bytes) which had functionality of originals but also could draw parametric graphs and had an icon menu.
The standard screen dimensions for these models is 16x8 characters ,
although the last line is only used for onscreen menus.
Initial Range 4.7,4.7,1,3.1,3.1 with 96x64 pixels.
Each character is 6x8 pixels. Physical screen dimensions: 51x34mm
Exceptions are 9700GE, 7300G, 6300G, 6000G. The 9700GE is larger than standard with 21x8 characters with initial Range 6.3,6.3,1,3.706,3.706,1 with 128x64 pixels which is 2 pixels wider than fitting in 21 characters. Physical screen dimensions: 58x34mm The 7300 has 13x6 characters with initial xrange 3.9. yrange automatic. with 80x64 pixels. Physical screen dimensions: 45x27mm The 6300 has only one character display line. (There is also the 6200 which is like the 6300 but without the programming facility) The 6000 has half the screen size 96×32 pixels. (There is also the 6500 which is like the 6000 but also has hyperbolic functions) 
The Power Graphics introduced: communications port; polar,parametric and inequality graphs; box and factor zoom; multiple graph scrolling; range initialization; integration; matrix mode; fractions; permutations; combinations; normal probabilities; SI unit symbols;
The Icon Menu Power Graphics introduced: numerical differentiation; matrices in programs; equation solver; dynamic graph mode;
The 24K Models introduced: complex numbers; table mode; more advanced equation solver; larger matrices (255x255); sigma calculations; graph solver for roots,intercepts,max &mins.
Also made were various nongraphic but programmable calculators such as the fx3950P, fx3650P,fx5500LA, fx4800P, fx4500PA,fx4200P, fx3900Pv and fx3600Pv which have a similar programming language. For more info on these see: www.rskey.org/casio.html