I have 2 scientific calculators.  The first calculator is Casio fx-120 which was given by my father as a toy when I was in primary school.  I bought my second scientific calculator Casio fx-570s when I was studying Additional Mathematics in secondary school.  The fx-120 is more than 25 years old, and the fx-570s is more than 15 years old.  Both of them are not functioning properly now.  :(

Before I studied about Sine, Cosine, Tangent, Log etc. in school, I was curious about them.  But calculator was just like a black box, I randomly keyed-in the inputs, and get the outputs.  Sometimes it was interesting when I get “Err” (Error) on the calculator.  I really enjoy playing with them.

Since it is not working properly, I unscrewed it and I discovered fx-120 has a 17-pin connector.  I searched from the web but the results did not answer my question on what this connector is meant for.  From a webpage, it says that the connector “may be” an extension to connect to a printer.  I have other guess, such as connect to external digit display or connect to external memory.

Tell me if you know the answer.

Fx-570s is also a discontinued product.  I like the way it interacted with human, but I cannot find it anymore.

I bought it in an electrical appliances shop, and a few years later I worked in that shop while waiting for my exam results.  I don’t think the boss remembered that I had bought a calculator from her.  I also did not tell her about it.

One day while I was serving a customer who wanted to buy scientific calculator, he looked at this model and suddenly he press some buttons and a hidden mode came out.  I think if this hidden mode is known by the board of exam, this calculator might be banned from the exam.  I have learned from that person how to activate the hidden mode, but I did not use it in the exam because the exam was over.  :P

This hidden mode can solve the simultaneous equation (Malay: persamaan serentak).  I believe the function was pre-built in the processor’s chip, but the calculator designers did not create a menu to access it nor documented it in the manual, because it might be built according to school exam specification in 1990’s.

Surprisingly, pressing 3 buttons (0, 1 and mode) at the same time can make this mode appear.  It can solve the following mathematical problem:-

ax + by + c = 0
dx + ey + f = 0

After entering a to f, it will give the answer of x and y.

Another thing that I like to play with this calculator is to see how slow it is.  I can create a problem for this calculator and it only gives me the answer after about 15 seconds.  The way to do it is Press [Sin] or [Cos] for 20 times (max it can support) and press a long number then press “=“.

This is to calculate sin(sin(cos(cos( …..sin(123456789))…. ))))).  The calculator will take a significant length of time to perform the calculation.

Hmm…  I am a tough calculator user right?

Which model would be my 3rd scientific calculator?  May be I would get a graphic scientific calculator.  Or I would use my abacus as scientific calculator?