Adding into stack
procedure add(item : items);
procedure delete(var item : items);
These two procedures are so simple that they perhaps need no more explanation. Procedure delete actually combines the functions TOP and DELETE, stackfull and stackempty are procedures which are left unspecified since they will depend upon the particular application. Often a stackfull condition will signal that more storage needs to be allocated and the program re-run. Stackempty is often a meaningful condition.
procedure addq (item : items);
procedure deleteq (var item : items);
{add item to the global stack stack;
top is the current top of stack
and n is its maximum size}
begin
if top = n then stackfull;
top := top+1;
stack(top) := item;
end: {of add}
Deletion in stack
{remove top element from the stack stack and put it in the item}
begin
if top = 0 then stackempty;
item := stack(top);
top := top-1;
end; {of delete}
Addition into a queue
{add item to the queue q}
begin
if rear=n then queuefull
else begin
rear :=rear+1;
q[rear]:=item;
end;
end;{of addq}
Deletion in a queue
{delete from the front of q and put into item}
begin
if front = rear then queueempty
else begin
front := front+1
item := q[front];
end;
end; {of deleteq}
