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Casio FX-702P

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I believe that the FX-702P was one of the very first BASIC programmable handheld calculators made by Casio. This early machine has several unique distinguishing features. First, its external interface is a 7-pin plug that is identical to that used on the fx-602P, and decidedly different from the wider plugs used in many later machines. Second, its programming model: it includes non-standard keywords such as INP or PRT, and a rich set of scientific functions (e.g., hyperbolic functions, 2-variable statistics) not normally found on BASIC handhelds. Even its keyboard layout is different: instead of a QWERTY layout, letters of the alphabet are arranged in sequential order.

That said, I kind of like this machine. Maybe it's that "retro" spirit in me, but I find this machine more friendly than later, slimmer Casio models.

Since this machine has a built-in hyperbolic sine function, it is only appropriate to demonstrate its programming model using an approximation of the logarithm of the Gamma function, developed by Robert H. Windschitl, which uses the hyperbolic sine for a fast and efficient computation:

10 INP "X",X
20 G=1
30 S=SGN X
40 Z=ABS X
50 IF Z>9 THEN 90
60 G=G*Z
70 Z=Z+1
80 GOTO 50
90 G=LN (Z*SQR (Z*HSN (1/Z)+1/810/Z^6))*Z-Z+LN (2*/Z)/2-LN G
100 IF S>0 THEN 120
110 G=LN (-/X/SIN (*X))-G
120 PRT G,EXP G