第27部分(第5/7 頁)

ut　ever　intending　to　do　so。　That　suggested　the　unintentional　code　was　probably　a　substitution　code；　with　numbers　for　letters。　When　I　got　the　word　breaks；　I　began　to　try　and　match　numbers　to　letters　by　frequency　analysis。　In　frequency　analysis　you　break　down　codes　by　using　the　fact　that　the　most　mon　letter　in　English　is　'e；'　and　the　second　most　mon　letter　is　't；'　and　so　on。　So　I　looked　for　the　most　mon　numbers。　But　I　was　impeded　by　the　fact　that　even　a　short　number　sequence；　such　as　two…three…two；　might　represent　many　code　possibilities：　two　and　three　and　two；　twenty…three　and　two；　two　and　thirtytwo；　or　two　hundred　and　thirty…two。　Longer　code　sequences　had　many　more　possibilities。〃

Then；　he　said；　he　was　sitting　in　front　of　the　puter　thinking　about　the　spiral　messages；　and　he　suddenly　looked　at　the　keyboard。　〃I　began　to　wonder　what　an　alien　intelligence　would　make　of　our　keyboard；　those　rows　of　symbols　on　a　device　made　to　be　pressed。　How　confusing　it　must　look　to　another　kind　of　creature！　Look　here；〃　he　said。　〃The　letters　on　a　regular　keyboard　go　like　this。〃　He　held　up　his　＇＇182＇＇　pad。

1 2 3 4 5 6 7 8 9 0

tab Q W E R T Y U I O P

caps A S D F G H J K L ；

shift Z X C V B N M ； 。 ？

〃And　then　I　imagined　what　the　keyboard　would　look　like　as　a　spiral；　since　our　creature　seems　to　prefer　spirals。　And　I　started　numbering　the　keys　in　concentric　circles。

〃It　took　a　little　experimentation；　since　the　keys　don't　line　up　exactly；　but　finally　I　got　it；〃　he　said。　〃Look　here：　the　numbers　spiral　out　from　the　center。　G　is　one；　B　is　two；　H　is　three；　Y　is　four；　and　so　on。　See？　It's　like　this。〃　He　quickly　penciled　in　numbers。

1 2 3 4 5 612 711 9 9 0

tab Q W E R13 T5 Y4 U10 1 O P

caps A S D14 F6 G1 H3 J9 K L ；

shift Z