The Stack Data Structure

Table of Contents

• Table of Contents
• 1. The Stack Data Structure
  • 1.1. Definition
  • 1.2. Algorithm for PUSH and POP Operations
    • 1.2.1. Declaration
    • 1.2.2. Algorithm

1. The Stack Data Structure

1.1. Definition

A linear abstract data structure where the elements could be added or deleted only at one open end, called the top of the stack.

• The elements follow “The Last In First Out Order”, typically called LIFO.
• Insertion into the stack is called a push operation, and deletion from the stack is called a pop operation.
• If the stack is full, it is said to be in the "Overflow" stage, and push is rejected if the stack is overflow.
• If the stack is empty, it is said to be in "Underflow" state, and pop is rejected if the stack is underflow.

1.2. Algorithm for PUSH and POP Operations

1.2.1. Declaration

Let S be a stack of SIZE = 100 elements, and TOP is an integer to hold the index of the last inserted element into the stack. Initially, TOP = -1

1.2.2. Algorithm

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1. PROCEDURE PUSH (v)
2.    IF TOP == SIZE – 1 THEN
3.        DISPLAY "STACK OVERFLOW"
4.        EXIT PUSH
5.    END IF
6.    TOP = TOP + 1 // INCREMENT THE TOP OF THE STACK BY 1
7.    S[TOP] = v // ASSIGN THE ELEMENT AT THE TOP OF THE STACK
8. END PROCEDURE PUSH

9. PROCEDURE POP ()
10.    IF S.TOP == -1 THEN
11.        DISPLAY “STACK UNDERFLOW”
12.        EXIT POP
13.    END IF
14.    v = S[TOP]
15.    TOP = TOP – 1
16.    RETURN v
17. END PROCEDURE POP