4. A stack is a data linear data structure in which addition of new element or deletion of an existing element always takes place at the same end. This end is called as top of the stack When an item is added to a stack, the operation is called as push when an item is removed from the stack, the operation is called as pop stack is also called as last–in-first-out (LIFO).

5. PUSH POP

6. PUSH (stack[MAX_SIZE],item) : This algorithm an item at the top of the stack[MAX_SIZE]. STEP-1: Initialize Set top = -1 STEP-2: Repeat step-3 to 5 until top<MAXSIZE-1 STEP-3: Read item STEP-4: Set top=top+1 STEP-5:Set stack[top]=item STEP-6:Print “stack overflow”

7. int stack[5], top = -1; void push( ) { int item; if (top<=4) { printf(“\n Enter the number”); scanf(“%d”, &item); top=top+1; stack [top] = item; } else { printf(“\n stack overflow”); }

10.  objects : a finite ordered list with zero or more elements.  functions: for all stack € Stack, item € element, maxStackSize € positive integer. Stack CreateS(maxStackSize)::= create an empty stack whose maximum size is maxStackSize Boolean IsFull( stack, maxStackSize )::= if(number of elements in stack==maxStackSize) return TRUE else return FALSE

11. Stack Push( stack, item)::= if(IsFull(stack))stack Full else insert item into top of stack and return. Boolean IsEmpty(stack)::= if(stack==CreateS( maxStackSize ) return TRUE else return FALSE Element Pop(stack)::= if(IsEmpty(stack))return else remove and return the element at the top of the stack.

12.  Direct applications  Page-visited history in a Web browser  Undo sequence in a text editor  Saving local variables when one function calls another, and this one calls another, and so on.  Indirect applications  Auxiliary data structure for algorithms  Component of other data structures

14. Queue is a linear data structure that permits the insertion of new element at one end and deletion of an element at the other end. The end at which the deletion of an element takes place is called as front and the end at Which insertion of new element can take place is called as rear. Queue is also called as first-in-first-out (FIFO).

15. ENQUEUE BACKFRONT DEQUEUE

16. QINSERT (Queue[MAXSIZE],item) : This algorithm inserts an item at the rear of queue [MAXSIZE] STEP-1: Initialisation. set front = -1 set rear = -1 STEP-2: Repeat steps 3 to 5 until rear<MAXSIZE -1 STEP-3: Read item STEP-4: If front = = -1 then

17. front = 0 rear = 0 Else rear = rear + 1 STEP-5: Set Queue [Rear] = item STEP-6: Print, Queue overflow

18. int queue [5], front = -1, rear = -1 ; Void queue ( ) { int item ; if (rear < 4) { printf(“\n Enter the number ”); scanf(“%d ” & item ); if (front = = -1 ) { front = 0 ; rear = 0; }

19. else { rear = rear + 1 ; } queue [rear] = item ; } else { printf (“\n Queue is full”); }

20. QDELETE (queue [MAXSIZE], item ) : This algorithm deletes an item at the front of the queue [MAXSIZE]. STEP-1: Repeat steps 2 to 4 until front >= 0 STEP-2: Set item = queue [front] STEP-3: If front = = rear set front = -1 set rear = -1 else front = front + 1

21. STEP-4: Print “ Number deleted is ”, item STEP-5: print “ Queue is empty ”

22. int queue [5], front, rear ; void delete ( ) { int item ; If ( front ! = -1) { item = queue [front]; if (front = = rear ) { front = -1; rear = -1 ; }

23. front = front +1 ; } printf (“\n Number deleted is = %d “, item ); } else { printf( “ Queue is empty”); }

24. ADT Queue is objects: a finite ordered list with zero or more elements. functions: for all queue € Queue,item € element,maxQueueSize € positive integer

25. Queue CreateQ(maxQueueSize)::= create an empty queue whose maximum size is maxQueueSize Boolean IsFullQ(queue,maxQueueSize)::= if(number of elements in queue==maxQueueSize) return TRUE else return FALSE

26. Queue AddQ(queue,item)::= if(IsFullQ(queue))queueFull else insert item at rear of queue and return queue Boolean IsEmptyQ(queue)::= if(queue==CreateQ(maxQueueSize)) return TRUE else return FALSE

27. Element DeleteQ(queue)::= if(IsEmptyQ(queue)) return else remove and return the item at front of queue.

28. 1)Serving requests of a single shared resource (printer, disk, CPU),transferring data asynchronously (data not necessarily received at same rate as sent) between two processes (IO buffers), e.g., pipes, file IO, sockets. 2) Call center phone systems will use a queue to hold people in line until a service representative is free.

29. 3) When a resource is shared among multiple consumers. Examples include CPU scheduling, Disk Scheduling. 4) Buffers on MP3 players and portable CD players, iPod playlist. Playlist for jukebox – add songs to the end, play from the front of the list.