# Basic CS-Data Structures [3i Infotech Placement]: Sample Questions 6 - 6 of 52

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## Question 6

Data Structures

### Explanation

- Stack is a linear data structure for following a particular order in which the operations are performed.
- The order is LIFO (Last in First Out) or FILO (First in Last Out) .
## Basic Features of Stack

- Stack is an ordered list of similar data type.
- Stack is a LIFO structure.
- Push () function is used to insert new elements into the stack and pop () function is used to delete an element from the stack.
- Both are and deletion allowed only at one end of stack called Top.
## Stack Operations

- Push
- Pop

**Push operation**:

- Putting a new data element onto stack is known as a push operation.
**Steps of push operation**.- Check if the stack is full.
- If stack is full, generate an error and exit.
- Stack is not full, increment top to point next empty space.
- Add data element to the stack location, where top is pointing.
- Returns success.

### Algorithm for PUSH Operation

begin procedure push: stack, dataif stack is full

return null

endif

top top + 1

stack [top] data

end procedure

**Pop Operation**:

- Accessing the content while removing it from the stack is known as a pop operation.
- In array implementation of pop () operation, the data element is not actually removed
- Top is decremented to a lower position in the stack to next value.
### Pop Steps

- Check if the stack is empty
- Stack is empty, produces an error and exit.
- The stack is not empty, access the data element at which top is pointing.
- Decreases the value of pop by 1.
- Returns accessed element.

### Algorithm for Pop Operation

begin procedure pop: stackif stack is empty

return null

endif

data stack [top]

top top -1

return data

end procedure.

**Application of stack**:

- Balancing of symbol
- Infix to postfix
- Redo-undo features at many places like editors, Photoshop.
- Forward and backward feature in web browsers.