Description of Stack in C language.

1. BRAINWARE
UNIVERSITY
STACK
NAME : RITU SARKAR
STUDENT CODE : BWU/BTD/21/010
STREAM : B.TECH CSE(DS)
COURSE : DATA STRUCTURE & ALGORITHMS
COURSE CODE : ESCD302

2. CONTENT
• Introduction
• What is Stack
• Properties of Stack
• Example
• Representation of Stack
• Operations of Stack
• Conditions of Stack
• Stack Implementation Using Array
• Stack Implementation Using Linked List
• Applications of Stack
• References
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3. INTRODUCTION
Data Structure is the representation of the logical relationship between individual elements of data. In Computer
Science, Data Structure is defined as a mathematical or logical model of organizing the data items into computer
memory in such a way that they can be used efficiently.The purpose of studying data structure is to learn how to
organize data into memory so that it can be accessed quickly and conveniently.
Data
Structure
Primitive
Int Float Char Pointer
Non-
Primitive
Linear
Sequential
Array Stack Queue
Linked
Linked
List
Linked
Stack
Linked
Queue
Non-
Linear
Graph Tree
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4. WHAT IS STACK
A stack is one of the most important and useful non-primitive linear data structure in computer science. Real-life
examples of the stack are a stack of books, a stack of plates, a stack of cards, a stack of coins, etc.
Definition: A stack is a sequential collection of elements into which new elements are inserted and from which,
elements are deleted only at one end.
PROPERTIES OF STACK
 It is an abstract data type.
 It is a First-In-First-Out (FIFO) data structure.
 It can be implemented using array as well as linked list.
 It has two main operations – Push ( insertion ) & Pop ( deletion ).
 In stack insertion and deletion is done at a single end that is a specific position, and
the position is called top.
A stack is declared as –
𝑑𝑎𝑡𝑎𝑡𝑦𝑝𝑒 𝑠𝑡𝑎𝑐𝑘𝑛𝑎𝑚𝑒[𝑠𝑖𝑧𝑒]
𝑖𝑛𝑡 𝑠𝑡𝑎𝑐𝑘 6
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5. EXAMPLE
OPERATIONS OF STACK
There are two main operations in stack data structure –
 Creation Operation
 IsemptyOperation
 Isfull Operation
 Push Operations
 Pop Operations
 Peek Operation
The stack can be represented using the following structure:
𝑠𝑡𝑟𝑢𝑐𝑡 𝑆𝑇𝐴𝐶𝐾
{
𝑖𝑛𝑡 𝑎 𝑀𝐴𝑋𝑆𝐼𝑍𝐸 ;
𝑖𝑛𝑡 𝑡𝑜𝑝;
};
REPRESENTATION OF STACK
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6. Operation Description
Creation This operation creates a stack and initializes the stack.
Isempty This operation checks whether the stack empty or not.
Isfull This operation checks whether the stack full or not.
Insertion (Push) This operation inserts an item only at the top of the stack when the stack is
not full.
Deletion (Pop) This operation deletes an item only at the top of the stack when the stack is
not empty.
Peek This operation returns the value of the top of the stack without removing
the element from the stack.
• Top = integer variable that points to the top location of the stack.
• Top = -1 ( If there is no data in the stack )
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7. Ex : int stack, push 10
push 20
pop
push 55
push 50
pop ; What is the top & the top value ?
⇒
10
20
10 10
55
10
50
55
10
55
10
5
4
3
2
1
0
5
4
3
2
1
0
5
4
3
2
1
0
5
4
3
2
1
0
5
4
3
2
1
0
5
4
3
2
1
0
5
4
3
2
1
0
push 10
→ → → → → →
push 20 pop push 55 push 50 pop
So, the top is 1 and the top value is 55.
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8. CONDITIONS OF STACK
There are two conditions in stack –
 Overflow Condition :
𝑖𝑓 (𝑇𝑜𝑝 == 𝑀𝑎𝑥𝑖𝑚𝑢𝑚 𝑆𝑖𝑧𝑒)
(𝑇𝑜𝑝 ≥ 𝑛)
When we can not insert any data as the stack is
filled, the state is called overflow condition.
11
66
55
43
33
22
 Underflow Condition :
𝑖𝑓 (𝑇𝑜𝑝 == −1)
When we can not delete any data as the stack is empty, the
state is called underflow condition.
5
4
3
2
1
0
5
4
3
2
1
0
push 10 pop
Ex :
Ex :
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9. STACK IMPLEMENTATION USING ARRAY
The array can be used to implement a stack of fixed size.
 Algorithm to insert (push) onto the stack :
Algorithm : PUSH (STACK, ITEM)
[STACK is an array of MAXSIZE and ITEM is an item to be
pushed onto stack]
1. [Check for stack overflow]
IfTOP = MAXSIZE - 1 then
a) Print: Overflow
b) Return
2. ELSE [Increase top by 1]
SetTOP =TOP + 1
3. [Insert item in new top position]
Set STACK[TOP] = ITEM
4. Return
 Algorithm to deletes (pop) the top element from the stack
Algorithm : POP (STACK, ITEM)
[STACK is an array and ITEM is an item to be popped from
stack]
1. [Check for stack underflow]
IfTOP = -1 then
a) Print: Underflow
b) Return
2. ELSE[Assign top element to item]
Set ITEM = STACK[TOP]
3. [Decrease top by 1]
SetTOP =TOP - 1
4. Return
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10. STACK IMPLEMENTATION USING ARRAY
The array can be used to implement a stack of fixed size.
 Algorithm of the push operation using linked list :
Algorithm : PUSH (HEAD, ITEM)
[HEAD is a pointer to the first node and ITEM is an item to
be pushed onto stack]
1. [Create the new node]
Allocate memory for NEW node
2. If NEW = NULL then
i) Print: Out of memory
ii) Return
3. Set NEW→DATA = ITEM
4. Set NEW→LINK = HEAD
5. Set HEAD = NEW
6. Return
 Algorithm of pop operation using linked list :
Algorithm : POP (HEAD, ITEM)
[HEAD is a pointer to the first node and ITEM is an item to be
popped from stack]
1. [Whether List is empty]
If HEAD = NULL then
i) Print: Stack is underflow
ii) Return
2. ITEM = HEAD→DATA
3. Set P = HEAD
4. HEAD = HEAD→LINK
5. Set P→LINK = NULL
6. De-allocate memory for node P
7. Return
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11. APPLICATIONS OF STACK
The stack is a very useful data structure. Most of the modern computers and microprocessor provide an inbuilt
hardware stack. Even there are stack-oriented computer architectures.
Stacks are used -
 To implement recursive function call and processing of function calls
such as passing arguments.
 Evaluation of Arithmetic expressions.
 To simulate recursion.
 To implement scope rule and block structure.
 To develop Compilers, System programs,Operating Systems and in
many elegant application algorithms.
 To implement different algorithms, Depth first search, Quicksort,
Mergesort etc.
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12. REFERENCES
 Class notes
 AText Book – Data Structure & Algorithm with C
– By Debdutta Pal, Suman Halder
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13. THANK YOU
Have A Great Day !
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Ritu Sarkar
bwubtd21010@gmail.ac.in