1 ss  [Seed of the random number generator.]sz

[*
 * lrx -- (number)
 * Push a random number from 1 to 20.
 *]sz
[
 [                [If preventing modulo bias:]sz
  sz               [Drop this random number.]sz
  lLx              [Loop.]sz
 ]SI
 [                [Loop:]sz
  [*
   * Formula (from POSIX) for random numbers of low quality.
   * Push a random number from 0 to 32767.
   *]sz
  ls 1103515245 * 12345 + 4294967296 % ss
  ls 65536 / 32768 %

  d 32768 20 % >I  [Prevent modulo bias.]sz
 ]d SL x
 20 % 1 +         [Be from 1 to 20.]sz
 LLsz LIsz        [Restore L, I.]sz
]sr


5 sb           [b = Total rows]sz
5 sc           [c = Total columns]sz

[Fill array a[] with random numbers from 1 to 20.]sz
[              [Inner loop for j:]sz
 lrx            [Push random number.]sz
 li lc * lj +   [Push index of a[i, j].]sz
 :a             [Put in a[].]sz
 lj 1 + d sj    [j += 1]sz
 lc >I          [Loop while c > j.]sz
]sI
[              [Outer loop for i:]sz
 0 d sj         [j = 0]sz
 lc >I          [Enter inner loop.]sz
 li 1 + d si    [i += 1]sz
 lb >L          [Loop while b > i.]sz
]sL
0 d si         [i = 0]sz
lb >L          [Enter outer loop.]sz

[Find a 20.]sz
[              [If detecting a 20:]sz
 li lj + 3 + Q  [Break outer loop.]sz
]sD
[              [Inner loop for j:]sz
 li lc * lj +   [Push index of a[i,j].]sz
 ;a             [Push value from a[].]sz
 p              [Print value and a newline.]sz
 20 =D          [Detect a 20.]sz
 lj 1 + d sj    [j += 1]sz
 lc >I          [Loop while c > j.]sz
]sI
[              [Outer loop for i:]sz
 0 d sj         [j = 0]sz
 lc >I          [Enter inner loop.]sz
 [==
]P              [Print "==" and a newline.]sz
 li 1 + d si    [i += 1]sz
 lb >L          [Loop while b > i.]sz
]sL
0 d si         [i = 0]sz
lb >L          [Enter outer loop.]sz