An expression using **AND** or **OR** like this is called a *conditional expression*. An example using **OR** could be: ``` price=price_less_tax*(1.15 OR v$="zero rated") ``` Notice how **AND** tends to go with addition (because its default value is **0**), and **OR** tends to go with multiplication (because its default value is **1**). You can also make string valued conditional expressions, but only using **AND**.

x$ AND y has the value	{	x$ if y is non-zero
		"" if y is zero

So it means **x$ if y** (else the empty string). Try this program, which inputs two strings and puts them in alphabetical order: ``` 10 INPUT "Type in two strings"'a$,b$ 20 IF a$>b$ THEN c$=a$:a$=b$:b$=c$ 30 PRINT a$;" ";("<" AND a$ b OR c ``` nor is it ``` IF a<>b OR a<>c ```