View source for Casio FX-502P series

{{short description|Series of programmable calculators produced by Casio}}
{{ Infobox Calculator
| name         = CASIO FX-501P / FX-502P
| image        = 41-year-old Casio FX-502P is still working..jpg
| caption      = A 41-year-old FX-502P in working condition
| type         = [[Programmable calculator|Programmable]] [[Scientific calculator|scientific]]
| entry        =[[Calculator input methods#Infix notation|Infix]]
| introduced   = 1978
| manufacturer = [[Casio]]
| display_type = [[Liquid crystal display|LCD]] [[seven-segment display]]
| precision    = 12 digits mantissa, ±99 exponent
| display_size = 10 + 3 Digits
| prog_lang    = [[Keystroke programmable|Keystroke]] <small>(fully merged, [[Turing completeness|Turing complete]])</small>
| memory_data  = 11 <small>(FX-501P)</small>, 22 <small>(FX-502P)</small>
| memory_step  = 128 <small>(FX-501P)</small>, 256 <small>(FX-502P)</small>
| conn1        = [[Compact Cassette]]
| via1_1       = [[Casio FA-1|FA-1]]
| ports        = one vendor specific
| supply       = 2×"G13" or 2×"LR44"
| power        = 0.0008&nbsp;W
| weight       = 141&nbsp;g, 5&nbsp;oz
| dimensions   = 15.24×7.6×1.2&nbsp;cm, 6"×3"×½"
}}
The '''FX-501P''' and '''FX-502P''' were [[programmable calculator]]s, manufactured by [[Casio]] from 1978/1979.{{cn|reason=Some web pages state 1978, those primary sources I have seen myself state 1979, I even found one web page stating 1976, so this needs to be narrows down in RS|date=June 2017}} They were the predecessors of the [[Casio FX-601P|FX-601P]] and [[Casio FX-602P|FX-602P]].

It is likely that the FX-501P/502P were the first LCD programmable calculators to be produced as up until 1979 (and the introduction of the HP-41C) no manufacturer had introduced such a device.

==Arithmetic==
The FX-502P series use [[algebraic logic]] as was state-of-the-art at the time.

==Display==
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, {{Citation needed span|text=supposedly to prevent ultra-violet radiation damage to the unstable (at the time) Liquid Crystal compound.|date=November 2018}}

They were the first Casio calculators to implement [[engineering notation]], and the first calculators in general to implement an engineering notation with shift facility (following [[Hewlett Packard]] calculators implementing the first [[engineering notation]] in general, and some [[Commodore Business Machines|Commodore]] and [[Texas Instruments]] calculators implementing [[variable scientific notation]] with exponent shift facility).

==Programming==
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.<ref>[http://fx-602p.krischik.com/index.php/Main/TokenCodes FX-602P Token list] - the FX-502P series only employed the standard plane.</ref>

The FX-501P could store 128 steps, with 11 memory registers. The FX-502P had twice that capacity with 256 steps and 22 memory registers.

Conditional and unconditional jumps as well as subroutines were 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 up of the digits 0 .. 9 and the character C, E, F and P. The calculator came with a special overlay<ref name="voidware">[http://www.voidware.com/calcs/fx501p.htm casio fx-501p with programming overlay]</ref> so the user did not need to memorize the mapping between code and actual command.

What differentiated the FX-501&nbsp;/ FX-502P from its competitors was that programming was retained in a battery-buffered memory when the calculator was turned off.

===Programming example===
Here is a sample program that computes the factorial of an integer number from 2 to 69. For 5!, the user would type <code>5</code> <code>P0</code> and get the result 120. The whole program is only 9 bytes long.

{| class="wikitable"
|-
! Key-code  !! Display-code !! Comment
|-
| {{keypress|P0}} || P0 || call the program with the P0 key
|-
| {{keypress|Min}}{{keypress|0}} || C6-00 || stores the value in register 0
|-
| {{keypress|1}} || 01 || starts with 1
|-
| {{keypress|LBL}}{{keypress|0}} || F0-00 || label for the loop
|-
| {{keypress|*}} || E1 || multiply
|-
| {{keypress|MR}}{{keypress|0}} || C7-00 || with M0
|-
| {{keypress|INV}} {{keypress|DSZ}} || FF-01 || Decrements M0 and skips next command if M0=Zero
|-
| {{keypress|GOTO}}{{keypress|0}} || F1-00 || Go to LBL0
|-
| {{keypress|1==}} || E5 || end of loop, the machine has calculated <math>1 \times n \times ( n - 1) \times \cdots \times 2 \times 1 =n!</math>
|}

==Interface==
{{ infobox computer hardware generic
| name         = Casio FA-1
| image        = Casio FA-1 interface.jpg
| type         = [[Compact Cassette]] Interface
| introduced   = 1979
| manufacturer = [[Casio]]
| conn1        = FX-502P series and [[Casio FX-602P series|FX-602P series]]
| conn2        = [[Compact Cassette]]
| via2_1       = Line-Out: 3.5&nbsp;mm [[TRS connector]]
| via2_2       = Mic-In: 3.5&nbsp;mm TRS connector
}}
The FX-501P and FX-502P used the [[Casio FA-1|FA-1]] to store program and data to [[Compact Cassette]] using the [[Kansas City standard]]. The FA-1 also enabled the calculators to generate musical notes.<ref name="voidware"/>

The FX-501P was used on the 1981 song "Pocket Calculator" by electronic music group [[Kraftwerk]].<ref>{{cite web|url=https://www.songfacts.com/facts/kraftwerk/pocket-calculator|title=Pocket Calculator by Kraftwerk|publisher=Songfacts|accessdate=1 May 2020}}</ref>

==References==
{{reflist}}

==External links==
* [http://casio.ledudu.com/pockets.asp?type=48&lg=eng FX-501P] and [http://casio.ledudu.com/pockets.asp?type=71&lg=eng FX-502P] on [http://casio.ledudu.com/pockets.asp?lg=eng casio.ledudu.com] maintained by ledudu.
* [http://casio.ledudu.com/casio502p/index.htm FX-502P Geek hosted by casio.ledudu.com]
* [http://www.rskey.org/detail.asp?manufacturer=Casio&model=fx-501P FX-501P] and [http://www.rskey.org/detail.asp?manufacturer=Casio&model=fx-502P FX-502P] on [http://www.rskey.org RS-Key] maintained by Viktor Toth.
* [http://www.voidware.com/calcs/fx501p.htm Casio FX-501P] and [http://www.voidware.com/calcs/fx502p.htm Casio FX-502P] on [http://www.voidware.com/calcs Voidware]
* [http://sim41.webcindario.com/sim502.htm FX-502P Simulator]
{{Casio-calc}}
{{Casio}}

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[[Category:Casio programmable calculators|FX-502P]]
[[Category:Products introduced in 1978]]