front of the sorter so that each card is visible and individually accessible (see fig structuring the cards as filehoweverimplies that from each pile only the card on the top is visible (see fig fig the sorting of file such restriction will evidently have serious consequences on the sorting method to be usedbut it is unavoidable if the number of cards to be laid out is larger than the available table before proceedingwe introduce some terminology and notation to be used throughout this if we are given items an- sorting consists of permuting these items into an array ak ak ak[ - such thatgiven an ordering function (ak < (ak << (ak[ - ]ordinarilythe ordering function is not evaluated according to specified rule of computation but is stored as an explicit component (fieldof each item its value is called the key of the item as consequencethe record structure is particularly well suited to represent items and might for example be declared as followstype item record keyinteger(*other components declared here*end the other components represent relevant data about the items in the collectionthe key merely assumes the purpose of identifying the items as far as our sorting algorithms are concernedhoweverthe key is the only relevant componentand there is no need to define any particular remaining components in the following discussionswe shall therefore discard any associated information and assume that the type item be defined as integer this choice of the key type is somewhat arbitrary evidentlyany type on which