# Arithmetic Expression in Data Structure

An expression is defined as a combination of some operands and operators. Three types of notation for expression are available:

## Infix Notation:

In this notation, operators are written in between the operands. The expression to multiply two numbers X and Y written in infix notation as :

**X*Y**

## Prefix Notation:

In this notation operators are written before the operands. Prefix notation is also called polish notation. The polish mathematician **Jan Lukasiewicz** developed this notation. The expression to multiply two numbers X and Y are written in prefix notation as:

***XY**

## Postfix Notation:

In this notation, operators are written after the operands. This notation is also called the reverse polish notation. The expression to multiply two X and Y is written in prefix notation as:

**XY***