Simple Types Are "struct" Types

This section describes simple types like 'int' and 'double'. Simple types are actually aliases of predefined 'struct' types which offers properties and methods.

Simple types are predefined, primary, and value based types, like "int", "long", "float", and "double". Unlike any other languages, C# has predefined "struct" type for each simple type, and provides the simple type as alias to the "struct" type. For example, "int" is aliased to System.Int32; "double" is aliased to System.Double.

In Java, there is one predefined Class for to each primary type. For example, Integer is defined for int; Double is defined for double. But int is not an alias to Integer.

Back in C#, if "int" is aliased to System.Int32, which is a "struct" type, an variable of "int" may actually occupy more 32 bytes in memory because of "struct" overhead. Can anyone approve that?

Some interesting features of simple types are shown in the following program:

// SimpleTypes.cs
// Copyright (c) 2015,, All Rights Reserved.

using System;
class SimpleTypes {
   public static void Main() {
      double d;
      System.Double dd;

      d = 10.0d/3.0d;
      dd = d;
      Console.WriteLine("d = {0}", d);
      Console.WriteLine("d.ToString() = {0}",d.ToString());
      Console.WriteLine("1.000.ToString() = {0}", 
      Console.WriteLine("System.Single.MaxValue = {0}",
      Console.WriteLine("System.Double.MaxValue = {0}",
      Console.WriteLine("System.Decimal.MaxValue = {0}",


d = 3.33333333333333
d.ToString() = 3.33333333333333
1.000.ToString() = 1
System.Single.MaxValue = 3.402823E+38
System.Double.MaxValue = 1.79769313486232E+308
System.Decimal.MaxValue = 79228162514264337593543950335

"1.000.ToString() = 1" shows that literals can be used as a variable to invoke its member method.

Last update: 2015.

Table of Contents

 About This Book

 Introduction of C# (C Sharp)

 Data Type and Variables

 Logical Expressions and Conditional Statements

 Arrays and Loop Statements

Data Type Features

 The "decimal" Data Type

Simple Types Are "struct" Types

 Type System Unification

 Jagged Arrays

 Floating-Point Data Types

 Passing Parameters to Methods

 Execution Environment Class

 Visual C# 2010 Express Edition

 Class Features

 C# Compiler and Intermediate Language

 Compiling C# Source Code Files

 MSBuild - Microsoft Build Engine

 Memory Usages of Processes

 Multithreading in C#

 Async Feature from C# 5

 System.IO.FileInfo Class

 System.Diagnostics.FileVersionInfo Class

 WPF - Windows Presentation Foundation

 Partial Classes and Partial Methods

 Outdated Tutorials


 PDF Printing Version