Calculator bugs

• Quotes and labels don't mix. To screw up someone else's program, simply enter an apostrophe, a quote and a newline or colon ('":) somewhere in the code. The calc will fail to find all labels following this, but the program will run. It will just fail inexplicably at the first `goto'. For example, try this prog:

  "HELLO"
  Goto 0
  '"
  Lbl 0
  1/0
  '"
  Lbl 0
  "WORLD"

  If the calc worked properly, this would give an error, due to the division by zero. What it actually does is print HELLO WORLD. This is because when it tries to understand the program, it recognises the apostrophe as a comment and jumps to after the next newline, colon or disp. When it looks for 'Lbl 0', however, it 'cunningly' ignores any which are inside strings. Or so Casio think. It thinks that everything between the two " signs is in a string, so it only finds the second 'Lbl 0', and carries on from there...

• If a newline character is put in the bottom-right of the screen, it loops around, so following lines are written over the top. The programs 'Amazing Face' and 'Text-based Noughts and Crosses' take advantage of this. These progs only work on fx-9700s, as they are written for a widescreen calc (this can be tweaked) and the bug was fixed for later calcs (accidentally, I suspect).

• Two double quotes ("") have no effect... unless they're done on the last line of the screen, in which case they replicate that line. e.g. "THIS APPEARS ONCE"
  "SO DOES THIS"
  ""
  "THIS DOES TOO"
  "AS DOES THIS"
  ""
  "AND THIS"
  "BUT..."
  "THIS APPEARS TWICE!"
  ""
  

  This was fixed (again accidentally, I suspect) for 9x50s onwards.

• If a comment ends in a triangle thingy, the value is displayed anyway. (I can't remember whether 'A_ displays the value of A or the Ans memory though. I think the rule is: display the value if possible, else display the Ans memory.)

  Thanks to Tom Wheeley for reminding me of that one.

• Toby Pereira found this one - On ICON MENU fx-9700s (and unknown others), if you press the MENU button during an operation which uses the graphics pointer (such as TRACE or allowing the user to select a point) and then hold down the left or right arrow key, it is still on the stupidly high graphics auto-repeat, so it shoots through the icons. Fixed for 9x50s.

• 9850 bug - If you try to scroll backwards too quickly while editing a large program, the scrolling jams and you have to restart (not reset) the calculator.

• NEW 9850 bug - No comments allowed between the If and Then of an If..Then..IfEnd construct.