CarolineW

    And here is my initial solution in UNIX shell:

    # bentley_knuth.sh

    # Usage:
    # ./bentley_knuth.sh n file
    # where "n" is the number of most frequent words 
    # you want to find in "file".
    
    awk '
        {
            for (i = 1; i <= NF; i++)
                word_freq[$i]++
        }
    END     {
                for (i in word_freq)
                    print i, word_freq[i]
            }
    ' < $2 | sort -nr +1 | sed $1q

    tr -cs A-Za-z '
    ' |
    tr A-Z a-z |
    sort |
    uniq -c |
    sort -rn |
    sed ${1}q

    C = (F-30) / 2
    F = 2 * C + 30

    C = (F-32) * 5 / 9
    F = C / 5 * 9 + 32

    C     F
  -40   -40
    0    32 (Approx water freezing point)
   10    50
   20    68 ( ~ 70)
  ~21    70
   30    86
   37    98.6 (body temperature)
   40   104
   50   122
  ...   ...
  100   212 (Approx water boiling point)