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Fundamentals of C#

Fundamentals of C#

Learn commonly used data types and operators in C#.

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Data types in C#

Every variable in C# needs to be declared with the help of a data type. It indicates whether a variable can store only numbers or can also store other symbols as its value.

Common data types

The following are the commonly used data types in C#:

  • int: Integer values (5, 0, -1, etc.)
  • double: Floating-point values (2.33333, -2500.001, 20.0, etc.)
  • bool: Boolean values (true, false).
  • char: Character values (a, 0, $ etc)
  • string: String values (educative, C#, etc.)

Variable declaration

The C# language requires the programmer to indicate the data type of the variables used in a program. The following code demonstrates the declaration of variables to input their values with suitable prompts and to display them with suitable labels:

class Test
{
    static void Main()
    {
        string str; // Declaring a variable of type string
        int number; // Declaring a variable of type integer
        double real; // Declaring a variable of type double
        bool isTrue; // Declaring a variable of type bool
        char letter; // Declaring a variable of type char

        System.Console.WriteLine("Please input a word: ");
        str = System.Console.ReadLine();
        System.Console.WriteLine("Please input an integer: ");
        number = int.Parse(System.Console.ReadLine());
        System.Console.WriteLine("Please input a real number: ");        
        real = double.Parse(System.Console.ReadLine());
        System.Console.WriteLine("Please input a boolean value true or false: ");
        isTrue = bool.Parse(System.Console.ReadLine());
        System.Console.WriteLine("Please input any character: ");
        letter = char.Parse(System.Console.ReadLine());

        System.Console.WriteLine("The value of each variable is enclosed in brackets: ");
        System.Console.WriteLine("str (" + str + ")");
        System.Console.WriteLine("number (" + number + ")");
        System.Console.WriteLine("fraction (" + real + ")");
        System.Console.WriteLine("isTrue (" + isTrue + ")");
        System.Console.WriteLine("letter (" + letter + ")");
    }
}
Variable declaration

Explanation

  • Lines 5–9: In these lines, the variables are declared so that they can be used to store values input by the user. There are different types of variables that are declared;
    • str is a variable of the string type.
    • number is a variable of the int type.
    • real is a variable of the double type.
    • isTrue is a variable of the bool type.
    • letter is a variable of the char type.
  • Lines 11–20: These lines output a prompt using System.Console.WriteLine(), demand input from the user using System.Console.ReadLine(), and then store them in the relevant variable.
  • Lines 22–27: These lines output the variable name as a label and the value enclosed in a bracket.

The following code demonstrates the declaration of the variables without inputting their values from the user:

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class Test
{
    static void Main()
    {
        string str; // Declaring a variable of type string
        int number; // Declaring a variable of type integer
        double real; // Declaring a variable of type double
        bool isTrue; // Declaring a variable of type bool
        System.Console.WriteLine("The value of each variable is enclosed in brackets: ");
        System.Console.WriteLine("str (" + str + ")");
        System.Console.WriteLine("number (" + number + ")");
        System.Console.WriteLine("fraction (" + real + ")");
        System.Console.WriteLine("isTrue (" + isTrue + ")");
    }
}

In the above code, lines 5–8 declare the variables str, number, real, and isTrue ...

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