1) A stack is a linear data structure that follows LIFO (last in, first out) ordering. Data is inserted using push operations and removed using pop operations. 2) A queue is a linear structure that follows FIFO (first in, first out) ordering. Data is inserted at the rear of the queue and removed from the front. 3) There are two main types of queues - linear and circular queues. Linear queues have separate front and rear pointers while circular queues connect the last position to the first to form a circle.

1. Stack & Queue
DATA STRUCTURES
Govt. Madhav Science College Ujjain
Department of Computer ScienceAnd application
PROF. ANIL KUMAR PRAJAPATI

2. What is a stack?
◦ Stack is linear data structure, working in last in first
out(LIFO) manner. It is an Abstract Data Type
(ADT), commonly used in most programming
languages.
◦ In this type of data structure, we can extract the
date from the end from which we enter the data.
◦ Push operation is used to enter data in stack and
pop operation is used to remove data.

3. Stack Representation
Top
Data Element
04
Data Element
03
Data Element
02
Data Element
01
Top
Data Element
04
Data Element
03
Data Element
02
Data Element
01
Data Element 05
Push
Data Element 05
Pop
Insertion Deletion

4. Algorithm for insert data into stack
Step 1. Check stack if full
If Top=Max-1
Print stack is full and exit
Step 2: Increment to by one
Top=Top+1
Step 3: Insert data into stack
Stack[TOP]=data
Step 4: End
1
2
1
3
2
1
4
3
2
1
5
4
3
2
1
Push
2
Push
3
Push
4
Push
5
Push
1
Max
size

5. Push (Insert data item into Stack)
For inserting data item into stack we use push operation.
Insertion
Top
Data 3
Data 2
Data 1
Data 1, Data 2, Data 3, Data 4, Data 5,
Insertion
Top
Data 4
Data 3
Data 2
Data 1
Insertion
Top
Data 2
Data 1
Insertion
Top
Data 1
Push

6. Algorithm for insert data into stack
Step 1: Check stack is empty
If TOP=-1
Print Stack is empty and Exit
Step 2: delete an element from stack top
Set Del_element=Stack[Top]
Step 3: decrement stack size by one
Top=Top-1
Step 4: End
5
4
3
2
1
4
3
2
1
3
2
1
2
1
Max
size Pop
5
Pop
4 Pop
3
1
Pop
2

7. Pop (Deleting data item from Stack)
for deleting data item into stack we use Pop operation.
Deletion
Top
Data 2
Data 1
Data 1, Data 2, Data 3, Data 4, Data 5,
Deletion
Top
Data 1
Deletion
Top
Data 3
Data 2
Data 1
Deletion
Top
Data 4
Data 3
Data 2
Data 1
pop

8. What is Queue
 A Queue is a linear structure which follows a particular order in
which the operations are performed. The order is First In First
Out (FIFO). In Queue the allocation of data are continuous
manner.
 insertion and deletion is done from different ends in the Queue,
using rear for insertion and front for Dilation.
 Queue having two different formats linear queue and circular
queue.

9. Types of Queue
broadly Queue are divided into two types such as linear and circular but
linear queue having also two different variations, double ended queue or
Dequeue and insertion restricted and deletion restricted.
10 20 30 40 50
Front
Rear
Linear Queue
10
50 30
20
40
60
Circular Queue
Rear
Front
10 20 30 40 50
10 20 30 40 50
Deletion restricted Queue
Double Ended Queue
Insertion restricted Queue
10 20 30 40 50
Rear
Front
Front
Rear
Front
Rear
Rear
Front
Rear
Front

10. Insertion Data item into Queue
Rear
Front
Front
Front
Front
Front
Rear
Rear
To insert data element into queue, we use rear pointer all data element inserted only rear end.
Algorithm for Insert an element into Queue
Step 1: Check if the queue is full.
If rear == max-size-1
Print Queue is full and exit
Step 2: Add and element into Queue
SET REAR = REAR + 1
Step 3: data element insert at rear pointer .
Set QUEUE[REAR] = NUM
Step 4: return success.
10
10 20
10 20 30
10 20 30 40
Rear
Rear
10 20 30 40 50
Rear
Front

11. Deletion Data item From Queue
Algorithm for Delete an element From Queue
Step 1: Check if the queue is Empty.
If FRONT == -1 or FRONT >REAR
Print Queue is Empty and exit
Step 2: Delete an data element from Queue
SET FRONT = FRONT + 1
Step 3: data element insert at rear pointer .
Set Data element = QUEUE[FRONT]
Step 4: return success.
To Delete data element from queue, we use front pointer all data elements delete
only front end.
10 20 30 40 50
Front
Rear
20 30 40 50
30 40 50
40 50
50
Front
Front
Front
Front
Rear
Rear
Rear
Rear

12. Circular Queue
Circular Queue is a linear data structure in
which the operations are performed based
on FIFO (First In First Out) principle and
the last position is connected back to the
first position to make a circle. Circular
queue also follow contiguous allocation of
data element. In the circular queue, for
insertion and deletion we use rear and front
pointer like linear queue

13. Thanks and Regards:
Anil Kumar Prajapati