Figure 6 The Quicksort Alogrithm in Pseudo-code

ALGORITHM QUICKSORT (ARRAY, FIRST, LAST)
  LOW = FIRST+1;
  HIGH = LAST;
  DO
    WHILE (ARRAY[LOW] <= ARRAY[FIRST] AND LOW <= LAST)
      LOW = LOW +1
    WHILE (ARRAY[HIGH] >= ARRAY[FIRST] AND HIGH > FIRST)
      HIGH = HIGH - 1
    IF HIGH > LOW
      exchange ARRAY[LOW] and ARRAY[HIGH]
  UNTIL LOW > HIGH
  exchange ARRAY[FIRST] and ARRAY[HIGH]
  IF (HIGH - FIRST) > 1 THEN
    QUICKSORT(ARRAY, FIRST, HIGH-1)
  IF (LAST - HIGH) > 1 THEN
    QUICKSORT(ARRAY, HIGH+1, LAST)
END OF ALGORITHM