The character encoding for the 5 bit search includes all the characters of the English alphabet (a-z, case independent) and a few selected "special" characters:

: ; , _ - .

"_" was chosen to stand in as a space to search for something like "do_it". For example: 

search string = "do_it" 
25-bit binary equivalent =   0010001111000000100110100 

search string found at binary index =  1884624304 
binary pi    : 0111110100100011110000001001101000000001000000001111111010111011 
binary string:         0010001111000000100110100                                
character pi    : ibkqma:xr-_:yi-.do_it_h_:z.tuo,ckv:,zu 
character string:                 do_it

In fact if you request a search for something with an imbedded space (" "), we replace the space with the underscore character, "_", so that it can be easily seen in the resulting string.

The other puncuation characters were selected to include some reasonable terminating characters that might be of interest. The encoding is fairly arbitrary. For example, the alphabetic characters could have as easily been reversed in their binary encoding or even randomized. Also we could have chosen, say, "!" instead of ":". Doing so would have allowed one to search for and find "do_it!" instead of "do_it:" as: 

search string = "do_it:" 
30-bit binary equivalent =   001000111100000010011010011111 

search string found at binary index =   752643884 
binary pi    : 1001111100100011110000001001101001111110101100111101000000110101 
binary string:         001000111100000010011010011111                           
character pi    : h.,uf-y-rd:;xt:do_it:usz_zrn.pvtytsyla 
character string:                do_it:

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