Lesson 9 Programming in Kotlin language Logical operations

      
Lesson 9 Programming in Kotlin language  Logical operations  

![Kotlin-logo.png]()

First, what is the Boolean variable: it is a variable that accepts only two values true, false

  Example 3> 2 The result is true

  7 <3 The result is false  

Logical operations: are( and - or – not) 

 For( and) we use &&  

For (or) we use ||

For (not) we use !                      
This table demonstrates logical operations 

![csharp-operators-arabic.jpg]()

the process( and) be true if and only if the value of both x and y is true 

 If either or both is false then the result is false

 the process (or) be false if and only if the value of each false is either one or both true, the result is true  

the process(not) is the opposite  

if the value of x is true--> the ! x is false

 if the value of x is false --> the !x is true

  for example: 

  fun main (args:Array <String>)

 { 

         print("enter a number: ")  

         var number1 = readLine()!!  

        print(number1>0 && number1<10)  

        print("enter other number: ")  

        var number2 = readLine()!!  

         print(number2 > 2 || number2 == 0)

 }

 In this example we asked the user to enter the number we stored in the variable (number1) if the number entered is greater than 0 and smaller than 10 then the result is true - if the two conditions are true – then otherwise the result will be false 

Then we dialed another number and stored it in(number2)  if the input number is greater than 2 or equal to 0. If either of the two conditions is true, the result is true.  If both are false, the result is false.   
Example:   

fun main (args:Array <String>)

 {  

       var x = 10    

      print((x > 1 && x <= 10) || (x > 50 && x < 100))

 }
In this example, we defined an x ​​variable of 10 The result that will be printed is true

  because if we replace each x with 10 of the condition we will be

  10> 1 --> true  

10 <= 10 --> true  

10> 50 --> false  

10 <100 -->true  

 the condition has become  ((true && true) || (false && true)) 

 We know that ( true && true) is true

  And ( false && true) is false 

 the result of The condition  (true) || (false)) is true  

I hope things are clear 

 We will understand the logical processes further in the next lesson, "Conditional Phrases" 

 Q: What will be the result in the previous example if it is  

var y = 20 

 var z = 55  

Instead of x