Casio FX-502P series
A 30-year-old Casio FX-501P in working condition displaying the number π
|Precision||12 digits mantissa, ±99 exponent|
|Display type||LCD Seven-segment display|
|Display size||10 + 3 Digits|
|Programming language(s)||Keystroke (fully merged, Turing complete)|
|Memory register||11 (FX-501P) 22 (FX-502P)|
|Program steps||128 (FX-501P) 256 (FX-502P)|
|Ports||one vendor specific|
Compact Cassette via:
|Power supply||2×"G13" or 2x"LR44"|
|Weight||141g, 5 oz|
|Dimensions||15.24x7,6x1.2 cm, 6"×3"×½"|
The FX-502P series use the algebraic logic as was state of the art at the time.
The FX-501P and FX-502P featured a single line 7-segment liquid crystal display with 10 digits as main display. An additional 3 digits 7-segment display used to display exponents and program steps when entering or debugging programs and 10 status indicators. The display was covered with a yellow filter, supposedly to prevent ultra-violet radiation damage.
The programming model employed was key stroke programming by which each key pressed was recorded and later played back. On record multiple key presses were merged into a single programming step. All operations fitted into one program step.
The FX-501P could store 128 steps, with 11 memory registers. The FX-502P had double capacity with 256 steps and 22 memory registers.
Conditional and Unconditional jumps as well as subroutines where supported. The FX-502P series supported 10 labels for programs and subroutines called P0 .. P9. Each program or subroutine could have up to 10 local labels called LBL0 .. LBL9 for jumps and branches.
The FX-501P and FX-502P supported indirect addressing both for memory access and jumps and therefore the programming model could be considered Turing complete.
Since the FX-501P and FX-502P only employed a Seven-segment display each program step was represented by a special 2 digit codes made op of the digits 0 .. 9 and the character C, E, F and P. The Calculator came with a special overlay so the user need not memorise the mapping between code and actual command.
What differentiated the 501/502P from its competitors was that programming was retained in a battery-buffered memory when the calculator was turned off. Texas Instruments And Hewlett Packard had comparable devices but without the constant memory capability.
Here is a sample program that computes the factorial of an integer number from 2 to 69. For 5!, you'll type
P0 and get the result, 120. The whole program is only 9 bytes long.
|P0||P0||You'll call the program with the P0 key|
|Min0||C6-00||stores the value in register 0|
|1||01||starts with 1|
|LBL0||F0-00||label for the loop|
|INV DSZ||FF-01||Decrements M0 and Skips next command if M0=Zero|
|GOTO0||F1-00||Go to LBL0|
|=||E5||end of loop, the machine has calculated|
|Type||Compact Cassette Interface|