To my no small pleasure, lately I began receiving Casio programmable calculators that significantly improve upon the programmability of their predecessors. Although the programming model is still unduly simplistic (the only kind of branching possible is a conditional jump back to the beginning of program space), these calculators offer more program memory and, most significantly, the ability to review and edit programs.

With 300 bytes to play with, I was able to write several implementations of my favorite programming example, the Gamma function for this machine. The example reproduced below uses Stirling's formula and a simple iteration to produce an accurate result even for small or negative arguments:

001 Kin 1
002 ×
003 (
004 Kout 2
005 -
006 Kout 3
007 +
008 1
009 Kin 3
010 )
011 =
012 Kin 2
013 5
014 Min
015 Kout 1
016 +
017 1
018 =
019 x<=M
020 Kin 1
021 ×
022 LN
023 -
024 Kout 1
025 +
026 (
027 2
028 ×
029 π 
030 ÷
031 Kout 1
032 )
033 LN
034 ÷
035 2
036 +
037 (
038 (
039 (
040 (
041 1
042 1
043 8
044 8
045 1/x
046 ÷
047 Kout 1
048 x²
049 -
050 1
051 6
052 8
053 0
054 1/x
055 )
056 ÷
057 Kout 1
058 x²
059 +
060 1
061 2
062 6
063 0
064 1/x
065 )
066 ÷
067 Kout 1
068 x²
069 -
070 3
071 6
072 0
073 1/x
074 )
075 ÷
076 Kout 1
077 x²
078 +
079 1
080 2
081 1/x
082 )
083 ÷
084 Kout 1
085 -
086 0
087 Kin 3
088 X-K2
089 LN
090 =