C# is a programming language developed by Microsoft in 2000. It was created as part of the .NET framework. C# code uses the .cs file extension and is compiled by the Common Language Runtime (CLR). The CLR handles memory management and other core tasks. C# supports object-oriented programming and type safety. A basic C# program structure includes using namespaces, declaring classes and methods. Common data types in C# include integers, floats, characters, booleans and strings. The language also supports user input/output, variable declaration using the var keyword, and defining constants.

1. C # (C Sharp)
Programming Language

2. History of C#
• Developed by Microsoft in 2000
• Anders Hejlsberg (Danish)
• Uses .cs Extension
• C# was developed by Anders Hejlsberg and
his team during the development of .Net
Framework.

3. .NET
• .NET is a free, cross-platform,
open source developer platform for
building many different types of
applications.
• With .NET, you can use multiple
languages, editors, and libraries to
build for web, mobile, desktop,
games, and IoT
Automatic Memory Management-
One of the biggest advantage of .net
framework is the built in memory
management.
.NET
CLR (Common Language Runtime)
Class library

4. ..
• CLR – CLR is the foundation of the .NET Framework. It
manages code at execution time, providing core services such
as memory management, code accuracy, and many other
aspects of your code.
• Class Library- It’s collection of classes , interfaces and value
types that enable you to accomplish a range of common
programming tasks such as data collection , file access and
working with text.

5. What is C#
• C# is a simple, modern, object-oriented, and type-safe
programming language.
• Type safety means that the compiler will validate types while
compiling, and throw an error if you try to assign the wrong type
to a variable.

6. Program Structure
using System;//use to include system namespace
namespace HellWorldApplication{ // namespace declaration is a collection of classes
class HelloWorld{ //class declaration
static void Main(string[] args){
Console.WriteLine("Hello World");
Console.ReadKey();//for vs.net users. Wait till user presses key.
}
}
}
Unlike Java, program file name could be different from the class
name.

7. Data Types
• int (16 bit, 32 bit(default), 64 bit)
• float
• char
• double
• bool
• string
int x= 42;
double pi= 3.14;
char y = 'z';
bool isOnline= false;
string name= "David";

8. User Input and Output
Input
static void Main(string[] args){
string yourName;
Console.WriteLine("What is your Name?");
yourName = Console.ReadLine();
Console.WriteLine("Hello {0}", yourName);
}
//Console.ReadLine() method returns a
string value.
If you are expecting another type of value
, the entered data must be converted to
that type.
This can be done using the Convert.ToXXX
methods. Ex-
Convert.ToInt64(Console.ReadLine());

9. var Keyword ( implicitly typed variables)
• A variable can be explicitly declared with its type before it’s
used.
• It’s handy function to enable the compiler to determine the type
of the variable automatically based on the expression it is
assigned to.
• Ex- var num= 15; // declared integer automatically

10. Constant
• Constant store value that cannot be changed from their initial
assignment. To declare a constant , use the const modifier.
• Example- const double pi = 3.14;