# Overview


- A stack is ta LIFO list. Meaning "last in first out"
- Access is allowed only from one end of the stack 
	- adding an item is called pulsing the stack 
	- retrieving an item is called popping the stack 

# Typical uses

- Parentheses matching; ()), or (())  
	- compiler's syntax check for matching braces is implemented by using stack

- The simplest application of a stack is to reverse a word.  
	• You push a given word to stack - letter by letter - and then pop letters from the stack.  

- Another application is an "undo" mechanism in text editors;  
	•this operation is accomplished by keeping all text changes in a stack

# Parenthesis count 

- Methodology (logical steps to solve the problem):  
	- scan expression from left to right;  
	- when a left parenthesis is encountered, add its position to the stack;  
- when a right parenthesis is encountered, remove matching position from stack (more example in a moment).  

# try-catch-throw

- When you enter a try block, push the address of this block onto a stack.  
\
- When an exception is thrown, pop the try block that is at the top of the stack; if the stack is empty, terminate the program.  

- If the popped try block has no matching catch block, go back to the previous step.  

- If the popped try block has a matching catch block, execute the matching catch block.