title: Logic of '12 days of christmas'
body: <p>Here is the well known example of obfuscated code in C generating lyrics of '12 days of christmas'. I tried to figure out the logic of the code that explains how actually the text is printed. But I am not able to understand the same.</p>
  
  <pre><code>#include &lt;stdio.h&gt;
  main(t,_,a)
  char *a;
  {
  return!0&lt;t?t&lt;3?main(-79,-13,a+main(-87,1-_,main(-86,0,a+1)+a)):
  1,t&lt;_?main(t+1,_,a):3,main(-94,-27+t,a)&amp;&amp;t==2?_&lt;13?
  main(2,_+1,"%s %d %d\n"):9:16:t&lt;0?t&lt;-72?main(_,t,
  "@n'+,#'/*{}w+/w#cdnr/+,{}r/*de}+,/*{*+,/w{%+,/w#q#n+,/#{l+,/n{n+,/+#n+,/#\
  ;#q#n+,/+k#;*+,/'r :'d*'3,}{w+K w'K:'+}e#';dq#'l \
  q#'+d'K#!/+k#;q#'r}eKK#}w'r}eKK{nl]'/#;#q#n'){)#}w'){){nl]'/+#n';d}rw' i;# \
  ){nl]!/n{n#'; r{#w'r nc{nl]'/#{l,+'K {rw' iK{;[{nl]'/w#q#n'wk nw' \
  iwk{KK{nl]!/w{%'l##w#' i; :{nl]'/*{q#'ld;r'}{nlwb!/*de}'c \
  ;;{nl'-{}rw]'/+,}##'*}#nc,',#nw]'/+kd'+e}+;#'rdq#w! nr'/ ') }+}{rl#'{n' ')#\
  }'+}##(!!/")
    :t&lt;-50?_==*a?putchar(31[a]):main(-65,_,a+1):main((*a=='/')+t,_,a+1)
      :0&lt;t?main(2,2,"%s"):*a=='/'||main(0,main(-61,*a,
  "!ek;dc i@bK'(q)-[w]*%n+r3#l,{}:\nuwloca-O;m .vpbks,fxntdCeghiry"),a+1);
  }
  </code></pre>
  
  <p>Can anyone guide me where can I find the explanation of this code snippet?</p>