CSharp – Variables and Data Types

CSharp – Variables and Data Types

Data types

You are required to inform the compiler about which data types you wish to use every time you declare a variable.

byte —> 0 .. 255

sbyte —> -128 .. 127

short —> -32,768 .. 32,767

ushort —> 0 .. 65,535

int —> -2,147,483,648 .. 2,147,483,647

uint —> 0 .. 4,294,967,295

long —> -9,223,372,036,854,775,808 .. 9,223,372,036,854,775,807

ulong —> 0 .. 18,446,744,073,709,551,615

float —> -3.402823e38 .. 3.402823e38

double —> -1.79769313486232e308 .. 1.79769313486232e308

decimal —> -79228162514264337593543950335 .. 79228162514264337593543950335

char —> a Unicode character.

string —> a string of Unicode characters.

bool —> true or false.

object —> an object.

Example with strings:

// Working with strings

using System;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            // <datatype> <name>
            string firstName = "John";
            string lastName = "Doe";

            Console.WriteLine("Name: " + firstName + " " + lastName);

            Console.WriteLine("Please enter a new first name:");
            // get new value from console 
            firstName = Console.ReadLine();

            Console.WriteLine("New name: " + firstName + " " + lastName);

            Console.ReadLine();
        }
    }
}

Example with math:

// Working with math

using System;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main()
        {
            // integer numbers
            int number1, number2;

            Console.WriteLine("Please enter a number:");
            // It reads a string and converts it into an integer. 
            number1 = int.Parse(Console.ReadLine());

            Console.WriteLine("Thank you. One more:");
            number2 = int.Parse(Console.ReadLine());

            Console.WriteLine("Adding the two numbers: " + (number1 + number2));

            Console.ReadLine();
        }
    }
}

Constants

The constants refer to fixed values that the program may not alter during its execution.

The syntax is:

const <data_type> <constant_name> = value;

Example:

using System;
using System.Collections;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            const double pi = 3.14159; // constant declaration 
            double r;
            Console.WriteLine("Enter Radius: ");
            r = Convert.ToDouble(Console.ReadLine());
            double areaCircle = pi * r * r;
            Console.WriteLine("Radius: {0}, Area: {1}", r, areaCircle);
            Console.ReadLine();
        }
    }
}