This poor Casio calculator almost drove me crazy. In fact, I am ashamed to admit, I was almost ready to hit it with something real hard, something I am usually very reluctant to do to my treasured machines.

Why, you ask? What brought out the vandal in me? Very simple... you see, every once in a while, for no apparent reason at all, this calculator responded with SN error to everything I typed. No apparent reason at all. I entered 10 X=1 and it accepted that program line. I entered 20 Y=2 and it was rejected.

Fortunately (for my own sanity and for the calculator's integrity) I discovered the reason just in time. You see, the big L-shaped key on the typewriter keypad and the key labelled ENTER on the numeric keypad do not have identical functionality. The numeric keypad's ENTER key is used to execute a line in calculator mode. For instance, typing 2*2 ENTER yields 4 on the display; but if you use the large key on the typewriter keyboard, the *2 part will be entered as BASIC line 2 in program memory.

I suspect that this was Casio's way of dealing with the lack of a MODE key which, on other Casio machines, switches between RUN and WRT modes...

The PB-700's programming model is similar to that of other Casio BASIC calculators, as demonstrated here by my favorite example, the Gamma function:

10 INPUT X
20 G=1
30 IF X>5 THEN 70
40 G=G*X
50 X=X+1
60 GOTO 30
70 G=X*LOGX-X+LOG(SQR(2*PI/X)/G)
80 G=G+((((1/99/X/X-1/140)/X/X+1/105)/X/X-1/30)/X/X+1)/12/X
90 PRINT G,EXPG