In addition to the array implementation, a stack can be implemented as a list. Since we have discussed two ways to implement lists, we know two ways to implement stacks as lists. One is to store the stack records in an array; the other is to store them in dynamic memory. We have already given an implementation of a stack using an array of records in Chapter 3梬here availist (Section 3.7) actually acts as a stack. When avail is invoked, it removes the top record from the availist, in addition to returning a pointer to the record. Thus it has effectively popped the record. Likewise, reclaim may return a record to the front of the availist. Doing so, reclaim is essentially pushing a new record onto the availist. Availist serves as the head of a list, which itself serves as a list implementation of a stack. Of course, appropriate overflow and underflow checking must be built into avail and reclaim, respectively.