# Algorithm Stack in VB.NET

A stack is an ordered list in which all insertions and deletions are made at one end, called the top.
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Stack

A stack is an ordered list in which all insertions and deletions are made at one end, called the top. Stack is a linear data structure which works based on the strategy last-in-first out (LIFO). A stack can have any abstract data type as an element, but is characterized by only two fundamental operations: push and pop. The push operation adds an item to the top of the stack, hiding any items already on the stack, or initializing the stack if it is empty It is a linear data structure which is open for operations at only one end (both insertions and deletions are defined at only one end). One natural example of stack, which arises in computer programming, is the processing of procedure calls and their terminations. Stacks are generally used to remember things in reverse. It finds a major use in backtracking approaches. Some of the functions related to a stack are

Create ( ) :- Q;

Insertion(Q, e) :- updated Q;

Deletion (Q) :- Q, e;

Isfull(Q) :- Boolean;

Isempty(Q) :- Boolean;

Top(Q) :- e;

Destroy(Q)

It has to be noted that with respect to a stack, insertion and deletion operations are, in general, called PUSH and POP operations respectively. Following are the algorithms for some functions of stack.

Algorithm: Create

Output: S, Stack created

Method
:

Declare S[SIZE] //Array of size=SIZE

Declare and Initialize T=0 //Top pointer to remember the number of elements

Algorithm ends

Algorithm: Isempty

Input: S, stack

Output: Boolean

Method:

If (T==0)
Return (yes)
Else
Return (no)
If end

Algorithm ends

Algorithm: Isfull

Input: S, stack

Output: Boolean

Method:

If (T==SIZE)
Return (yes)
Else
Return (no)
If end

Algorithm ends

Algorithm: Push

Input: (1) S, stack; (2) e, element to be inserted; (3) SIZE, size of the stack;
(4) T, the top pointer

Output: (1) S, updated; (2) T, updated

Method:

If (Isfull(S)) then
Print ('stack overflow')
Else
T=T+1;
S[T] =e
If end

Algorithm ends

Algorithm: Pop

Input: (1) S, stack;

Output: (1) S, updated; (2) T, updated (3) 'e' element popped

Method:

If (Isempty(S)) then
Print ('stack is empty')
Else
e = S[T]
T=T-1;
If end

Algorithm ends

Summary