• Integers (no fractional part) : Byte, Short, Int, Long
• Floating Point (with fractional part) : Float, Double

 fun main() {
	val byte: Byte = 1      // Size = 1B, Range = -128..127
	val short: Short = 1000 // Size = 2B, Range = -32k..32k
		
	val int = 5             // Size = 4B, Range = -2e9..2e9
	val long = 5L           // Size = 8B, Range = -9e18..9e18
		
	val float = 3.14f       // Size = 4B, upto 7 decimal digits
	val double = 3.14       // Size = 8B, upto 16 decimal deigits
}
 

Note that L is used to define Long, f is used to define Float and decimal point number without f is inferred as Double.

• We can assign numerical values in hexadecimal and binary format using 0x and 0b prefix :

   fun main() {
  		val bin = 0b101 // Binary number
      val hex = 0xFF // Hexadecimal number
      println(bin) // Prints "5"
      println(hex) // Prints "255"
  }
   

• To represent large numbers in a readable way, we can use underscores _ as :

   val billion = 1_000_000_000
   

• Char (stores single character)
• String (stores multiple characters)

 fun main() {
		val char = '#' // Size = 2B
		val string = "INDIA" // Size = 5 * 2B = 10B
}
 

Note that Char is enclosed in single quotes ‘’ while String is enclosed in double quotes “”.

Boolean is used to represent a 0/1 or true/false value :

 fun main() {
	val bool = true
	val bool2 = false
}
 

Collections are used to hold multiple values of similar type. Examples include :

• Arrays, Lists, Sets, Maps

We will learn more about Collections in Collections chapter.

Kotlin supports Object Oriented Programming. So using Classes, we can define our own data types. We shall learn more about OOPs in the OOPs chapter.

Unit is a special data type in Kotlin which holds no data.

Why do we need a data type that holds no data?

It is needed as a placeholder.

The most common usecase for Unit is in function return types. When a function returns no output, it actually returns Unit. All functions which have no return type defined, default to returning Unit.

Examples -

• println() function returns no output. If we print the output of println(), we get Unit :

   fun main() {
  		println(
  		    println("Namaste Unit") // Prints "Namaste Unit"
  		) // Prints "kotlin.Unit"
  }
   

• Lets define an empty function and print its output. As we discussed earlier, if a function’s return type is not defined, it defaults to returning Unit :

   fun alpha() { } // == fun alpha(): Unit
  
  fun main() {
      println(alpha()) // Prints "kotlin.Unit"
  }