**Polish Notations**

In the early 1920s, a Polish logician, Jan Lukasiewicz invented a special notation for prepositional logic that allows to eliminate all parenthesis from formulas. The notation is called Polish Notation, which results in a less readable expression. Depending upon the arrangement of operators and operands in an expression, Polish notation may be classified as:

- Infix Polish Notation
- Prefix Polish Notation
- Postfix Polish Notation

**Infix Polish Notation:** In this notation, the operator comes between two operands. For example: A+B, where A, B are operands and + is an operator.

**Prefix Polish Notation:** In this notation, the operator comes before two operands. For example: +AB.

**Postfix Polish Notation:** In this notation, the operator comes after two operands. For example: AB+.

**Application of Stacks:**

- Parenthesis checker
- Evaluation of Postfix expression
- Evaluation of Prefix expression
- Evaluation of Infix expression
- Conversion from Infix to Postfix
- Conversion from Infix to Prefix
- Conversion from Postfix to Prefix
- Conversion from Postfix to Infix
- Conversion from Prefix to Postfix
- Conversion from Prefix to Infix