Casio fx-602p

Courtesy of Ernst Mulder, original page.
Brand: Casio 
Model: fx-602p 
Type: Alphanumeric programmable scientific calculator 
Batteries: CR 2032 x 2 
Lifetime: Introduced: 1982
Terminated: unknown 
Notes: This is IMHO the best and most usable programmable calculator ever. The user interface is very good and clear, the display is fantastic and its interfacing options are adequate. This calculator came in two versions, the Casio fx-601p and the Casio fx-602p. The Casio fx-601 has 128 programming steps, the Casio fx-602 has 512 programming steps, more than enough for most tasks. This calculator is the successor to the non-alphanumeric Casio fx-501p and Casio fx-502p. The 601p/602p calculators were available next to their basic programmable brother the Casio fx-702p. 

A rather funny 'function' of this calculator is its ability to play music using its cassette interface. A special keyboard overlay for this function was also available and part of the standard package. The manual even listed a couple of songs that could be played in this manner! 

This calculator (as do many other Casio scientific calculators) uses one and the same key for both the constant π as well as exponents. This works as follows. When you first enter digits, the "EXP"-key will enable you to enter the numbers exponent, otherwise it will enter the constant π. 

Synthetic Programming
I've written a large number of programs for this calculator, some using all 512 steps of memory. Not many people know that "Synthetic Programming" is possible on this calculator by using a "mirror". The calculator had two working modes, alphanumeric and non-alphanumeric. The programming step to switch between the two modes is always automatically balanced, the step acts as a switch between the alphanumeric and non-alphanumeric mode. Now, to enter Synthetic Programming do the following: 
  1. Create a new program 
  2. With the following steps: " xxxxxxxxxxxxxxxxxx "

  3. (Just enter a large bulk of alphanumeric stuff, say 200 steps) 
  4. Now start erasing this program, but switch off the calculator before it finishes erasing your program 
  5. Create another new program 
  6. With random steps, until you encounter the remainder of your not-entirely-erased program, which will now end with an unbalanced alphanumeric switch! 
This switch will act as a "mirror". Look at your program from one end to enter alphanumeric steps, look at it from the other end to see all kinds of new instructions! This way it is also possible to enter all kind of normally unavailable alphanumeric symbols. 

My programs used to be full with these. The "mirror" could be saved to tape as well. 

There were some bugs in this calculator as well. To my mind come the following two: 
  • I can crash the calculator with only a few keystrokes. No programming necessary. 
  • When there was room for at least one more program, it can be used to write a simple 3-step program to look for passwords set for other programs. This one also makes use of the fact that the alphanumeric switch needs to be balanced.
Although this calculator is fast to begin with, it could easily be speeded up by simply changing the value of one of its internal resistors. Mine was at least twice as fast as it should be. I had to change batteries twice as often as well though... 
Full Reset
One of the e-mails I receive every now and again goes something like this: "I have a Casio fx-602p and love it, but suddenly I only have only n programming steps left instead of the usual 512, and I can't add any more programs in MODE 2". Well, the solution to this little problem is a simple one. Type the following key sequence: "MODE", "1", "MODE", ".", "2", "0", "MODE", "3", "MAC" and everything should be back to normal. Please note that this will completely clear the calculator's memory and any user programs are lost as well.