Such a node is allocated, enough storage is reserved to hold the largest possible variant of the record

such a node is allocated, enough storage is reserved to hold the largest possible variant of the recordin this case, pair of integers.However, suppose we know that the node will only contain a single integer. Then it is wasteful to reserve storage for two integers, since only one is necessary. To assist in conserving storage, Pascal allows another from of the new and dispose procedures. new(p, single) allocates a variable of type nodetype with only enough storage in the variant part of the record to contain a single integer, while new(p, pair) allocates a nodetype variable with enough storage in the variant part to contain two integers. The tag field sp is not assigned a value by the call to new. Subsequently, the tag field may only be assigned the value specified in the call to new and may not be changed. For its entire lifetime, such a record adopts a single one of its variantsA node created by the new function with two arguments must be freed with the dispose function using two arguments. dispose(p, single) is used to free a record created by new(p, single), while dispose(p, pair) is used to free a record created by new(p, pair). Similarly, if a variant record has more than one tag field (in the case of a variant record which contains a field that is itself declared as a variant record), new and dispose can be called with more than two arguments.Another restriction on a variant record variable created by the new function with more than one argument is that it cannot appear in an assignment statement. The reason for this is that an assignment statement is usually implemented by copying the contents of memory from one area to another. The amount of memory to be copied is determined from the types of the variable in the assignment. When a variant record is allocated with a specified tag value, it is not always possible to determine in advance (i.e., at compilation time) the size of the record and, therefore, the amount of memory to be copied. Although the source and the target of the assignment might be of the same type, they may be of different sizes since one might be allocated with a specific tag value (two parameters in the new function) and the other might be allocated with a different tag value r without any specific tag value (only one parameter in the new function). For this reason, standard Pascal prohibits such record assignments. Individual Pascal compilers might implement such assignments consistently correctly, inconsistently correctly, consistently, or not at all. Such assignments are therefore not recommended even if, on occasion, your complier does allow the assignment.Of course, individual fields of such variant record, including those fields present only in the allocated variant, may be assigned freely, subject only to the general Pascal type-agreement rules for assignment.Comparing the Dynamic and ArrayImplementations of Lists

It is instructive to examine the advantages and disadvantages of the dynamic and array implementations of linked lists. The major disadvantage