This document discusses stacks, which are non-linear data structures that follow the LIFO (last in, first out) principle. Stacks have operations like push and pop that insert and remove elements from the top of the stack. Pushing adds an element and increments the top pointer, while popping removes an element and decrements the top pointer. Stacks have applications in expression evaluation, memory management, and recursion. The document provides algorithms and code examples for implementing push and pop operations on a stack.

1. STACK
REPRESENTATION
BY- DIGVIJAY SINGH KARAKOTI

2. WHAT IS STACK?
Stack is the non-linear non-primitive data
structure or an ordered pair of elements.
A Stack is a LIFO structure which follows the
principal of “LAST IN FIRST OUT”, which
depicts the insertion of last element in the
stack and deletion of first element from the
stack from one end called “TOP” of the stack.

3. Some real life examples of
Stack

4. APPLICATIONS OF STACK
 Expression evaluation
 Infix, Prefix and Postfix Notation
 Expression conversion
 Memory Management
 Recursion

5. OPERATIONS PERFORMED IN
STACK
The m or oper at i ons per f or m by
aj
ed
st ack
ar e:
 PU ( ) – Thi s oper at i on i s used
SH
t o i nser t t he el em
ent i nt o t he
st ack. So, i t i s al so know as
n
“I N TI O ” oper at i on.
SER N
 PO ) - Thi s oper at i on i s used
P(
t o del et e or r et r i eve t he el em
ent

6. PUSH OPERATION
This function will add elements/items into
the stack. Whenever we add an element
into the stack the pointer TOP gets
incremented as:TOP+1 or TOP++
This is used to show the position of the
element in the stack.

7. PUSH operation on stack is to add values into the stack. Let us
assume that 5 items 30, 20, 25, 10 and 40 are to be placed on
the stack. The items can be inserted one by one as shown in
following figure:-

8. ALGORITHM FOR PUSH
OPERATIONITEM, TOP)
PUSH(MAXSTK,
STEP 1: If TOP = MAXSTK THEN [Stack already
filled?]
Print "OVERFLOW"
Go to step 4
End if
STEP 2: TOP = TOP + 1 [Increase TOP by 1]
STEP 3: Set STK[TOP] = ITEM [Insert ITEM in
new TOP position]

9. Program implementation of PUSH
operation
void push()
{ int item;
If(TOP==maxsize-1)
{ printf(“n Stack is full”);
getch();
exit(0);
}
else
{ printf(“n Enter the element to be inserted”);
scanf(“%d”, &item);
TOP=TOP+1;
stack[TOP]=item;
}
}

10. POP OPERATION
This function will delete elements/items
from the stack. Whenever we add an
element into the stack the pointer TOP
gets decremented as:TOP-1 or TOP-This is used to show the position of the
element in the stack

11. POP operation on stack is to delete or retrieve values from the
stack. Let us assume that 4 items 15, 12, 10 and 5 are to be
deleted from the stack. The items can be deleted one by one as
shown in following figure:-
Figure. Deletion operations

12. ALGORITHM FOR POP
OPERATION
POP[STACK,TOP,ITEM]
STEP 1: If TOP=0
Print ”Underflow”
STEP 2: Set ITEM=STACK[TOP]
STEP 3: Set TOP=TOP-1
STEP 4: Return

13. Program implementation of POP
operation
int pop()
{ int item;
if(TOP==-1)
{ printf(“n Stack is empty”);
getch();
exit(0);
}
else
{ item=stack[TOP];
TOP=TOP-1;
printf(“n Item deleted is= %d”, item);
}
return(item);
}