# 1. Introduction

One of the common requirements of the CPU is to be able to handle algebraic expressions such as

`4(3-2)*(5+6)`

We know that mathematical operators have *precedence - they have an order*. The brackets have to be evaluated first, then mulitply or divide and so on. Working with the example above we get :

`4(1)*(11)`

then deal with the left term we get:

`4*11`

Answer

`44`

This form of notation is called algebraic **'infix'** notation.

But CPUs do not evaluate expressions in this way. They use the 'stack' data structure to evaluate expressions, and infix notation is not compatible with a stack and so another method must be found.

This mini-web will take you through how a CPU handles mathematical expressions.

**Challenge** see
if you can find out one extra fact on this topic that we haven't
already told you

Click on this link: infix algebraic notation

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