This document discusses the implementation of a queue data structure in C programming language. It begins with an introduction to queues, describing them as open-ended data structures that follow a FIFO methodology. It then covers the basic queue operations of enqueue, dequeue, peek, isfull, and isempty. Algorithms and C code implementations are provided for each operation. The document aims to explain how queues work and can be created using arrays in C.

1. Queue
Presented by:
Kuljit Singh
BCA 3rd
2120786

2. TABLE OF CONTENTS
01
Introduction
03
02
Basic
Operation
Implementatio
n of Queue
in C

3. Introduction
01

4. Queue is an abstract data structure,
somewhat similar to Stacks. Unlike
stacks, a queue
is open at both its ends. One end is
always used to insert data (enqueue) and
the other
is used to remove data (dequeue).
Queue follows First-In-First-Out
methodology, i.e.,
the data item stored first will be accessed
QUEUE

5. As in stacks, a queue can also be
implemented using Arrays, Linked-
lists, Pointers and
Structures. For the sake of
simplicity, we shall implement
queues using one-dimensional
array.
Queue
Representation

6. Basic Operation
02

7. Basic operation
enqueue()
dequeue()
peek()
isfull() and
isempty()
QUEUE

8. Enqueue()
Queues maintain two data pointers, front
and rear. Therefore, its operations are
comparatively difficult to implement than
that of stacks.

9. PROCESS
If the queue is not
full, increment rear
pointer to point the
next empty
space.
Step 3
Check if the queue is
full.
Step 1
If the queue is full,
produce overflow
error and exit.
Step 2
Add data element to
the queue location,
where the rear is
pointing.
Step 4
Return success.
Step 5

10. procedure enqueue(data)
if queue is full
return
overflow endif
rear ← rear + 1
queue[rear] ← data
return true
end procedure
Algorithm for enqueue() operation

11. Implementation of enqueue() in C
programming language −
int enqueue(int data)
if(isfull())
return 0;
rear = rear + 1;
queue[rear] = data;
return 1;
end procedure

12. Dequeue()
Accessing data from the queue is a
process of two tasks − access the data
where front
is pointing and remove the data after
access.

13. If the queue is not
empty, access
the data where
front is pointing.
Step 3
Check if the queue
is empty.
Step 1
If the queue is
empty, produce
underflow error
and exit.
Step 2
Increment front
pointer to point
to the next
available data
element.
Step 4
Return success.
Step 5
Process

14. Algorithm for dequeue operation
procedure dequeue if
queue is empty
return
underflow end if
data = queue[front]
front ← front + 1
return true
end procedure

15. Implementation of dequeue() in C
programming language −
int dequeue() {
if(isempty())
return 0;
int data = queue[front];
front = front + 1;
return data;
}

16. Peek()
Gets the element at the front of the queue
without removing it.

17. Algorithm of peek()
function
begin procedure peek
return queue[front]
end procedure

18. Implementation of peek() function
in C programming language −
int peek() {
return queue[front];
}

19. Isfull()
Checks if the queue is full.

20. Algorithm of isfull() function −
begin procedure isfull
if rear equals to MAXSIZE
return true
else
return false
endif
end procedure

21. Implementation of isfull() function
in C programming language −
bool isfull() {
if(rear == MAXSIZE - 1)
return true;
else
return false;
}

22. Isempty()
Checks if the queue is empty.

23. Algorithm of isempty() function
begin procedure isempty
if front is less than MIN OR front is greater than rear
return true
else
return
false endif
end procedure

24. C programming code −
bool isempty() {
if(front < 0 || front > rear)
return true;
else
return false;
}

25. Implementation of Queue in C
03

30. The result will be

31. Please ask me if you have
queries
Thank you!!