[Calculation of Catalan numbers.
   EDSAC program, Initial Orders 2.]

  [Define where to store the list of Catalan numbers.]
            T   54 K  [store address in location 54, so that values
                       are accessed by code letter C (for Catalan)]
            P  200 F  [<------ address here]

  [Modification of library subroutine P7.
   Prints signed integer up to 10 digits, right-justified.
   54 storage locations; working position 4D.
   Must be loaded at an even address.
   Input: Number is at 0D.]
            T   56 K
  GKA3FT42@A47@T31@ADE10@T31@A48@T31@SDTDH44#@NDYFLDT4DS43@TF
  H17@S17@A43@G23@UFS43@T1FV4DAFG50@SFLDUFXFOFFFSFL4FT4DA49@T31@
  A1FA43@G20@XFP1024FP610D@524D!FO46@O26@XFO46@SFL8FT4DE39@

     [Main routine]
            T  120 K  [load at 120]
            G      K  [set @ (theta) to load address]
     [Variables]
      [0]   P      F  [index of Catalan number]
     [Constants]
      [1]   P    7 D  [maximum index required]
      [2]   P      D  [single-word 1]
      [3]   P    2 F  [to change addresses by 2]
      [4]   H     #C  [these 3 are used to manufacture EDSAC orders]
      [5]   T     #C
      [6]   V     #C
      [7]   K 4096 F  [(1) add to change T order into H order
                       (2) teleprinter null]
      [8]   #      F  [figures shift]
      [9]   !      F  [space]
     [10]   @      F  [carriage return]
     [11]   &      F  [line feed]

           [Enter with acc = 0]
     [12]   O    8 @  [set teleprinter to figures]
            T    4 D  [clear 5F and sandwich bit]
            A    2 @  [load single-word 1]
            T    4 F  [store as double word at 4D; clear acc]
           [Here with index in acc, Catalan number in 4D]
     [16]   U      @  [store index]
            L    1 F  [times 4 by shifting]
            A    5 @  [make T order to store Catalan number]
            U   27 @  [plant in code]
            A    7 @  [make H order with same address]
            U   45 @  [plant in code]
            S   47 @  [make A order with same address]
            T   34 @  [plant in code]
            A    6 @  [load V order for start of list]
            T   46 @  [plant in code]
            A    4 D  [Catalan number from temp store]
     [27]   T     #C  [store in list (manufactured order)]
            T      D  [clear 1F and sandwich bit]
            A      @  [load single-word index]
            T      F  [store as double word at 0D]
     [31]   A   31 @  [for return from print subroutine]
            G   56 F  [print index]
            O    9 @  [followed by space]
     [34]   A     #C  [load Catalan number (manufactured order)]
            T      D  [to 0D for printing]
     [36]   A   36 @  [for return from print subroutine]
            G   56 F  [print Catalan number]
            O   10 @  [followed by new line]
            O   11 @
            T    4 D  [clear partial sum]
            A      @  [load index]
            S    1 @  [reached the maximum?]
            E   64 @  [if so, jump to exit]
            [Inner loop to compute sum of products C{i}*C(n-1}]
     [44]   T      F  [clear acc]
     [45]   H     #C  [C{n-i} to mult reg (manufactured order)]
     [46]   V     #C  [acc := C{i}*C{n-i} (manufactiured order)]
           [Multiply product by 2^34 (see preamble). The 'L F' order is
            also exploited above to convert an H order into an A order.]
     [47]   L      F  [shift acc left by 13 (the maximum available)]
            L      F  [shift 13 more]
            L   64 F  [shift 8 more, total 34]
            A    4 D  [add partial sum]
            T    4 D  [update partial sum]
            A   46 @  [inc i in V order]
            A    3 @
            T   46 @
            A   45 @  [dec (n - i) in H order]
            S    3 @
            U   45 @
            S    4 @  [is (n - i) now negative?]
            E   44 @  [if not, loop back]
           [Here with latest Catalan number in temp store 4D]
            T      F  [clear acc]
            A      @  [load index]
            A    2 @  [add 1]
            E   16 @  [back to start of outer loop]
     [64]   O    7 @  [exit; print null to flush teleprinter buffer]
            Z      F  [stop]
            E   12 Z  [define entry point]
            P      F  [acc = 0 on entry]