My first C# program

Console output

Introduction to variables and int type

String type introduction

Brave new world

Computer hardware introduction

C# naming convention

Comments in C#

C# problems practice

The Mission

C# program structure

If statement

Visual Studio extension

Back to the streets

Bool type introduction

Console readline

Who is who

C# compilation process

Introduction to for loop

Find the basement

Introduction to double type

Introduction to char type

Talk in the big kitchen

Introduction to while loop

Introduction to methods

Repairing Noname

Introduction to arrays in C#

Lists

Introduction to scopes

Victory is close

Constants in C#

Wonderland

Input validation

Modulo operation

Career raise opportunity

Type conversion

Passing parameters to functions

Infinity

Switch statement

C# test

The truth

Class and object

Access modifiers

Hello, Wonderland

Static keyword

Null and this keywords

I will be your spy

Properties

Encapsulation

The Commander

Exceptions in c sharp

Going deeper in C# Exceptions

A Secret Server

Introduction to inheritance

Keywords override sealed and object

The Mystery of the old server

Interfaces in C#

Polymorphism

One step ahead

C# Core

C# core course

Sometimes I think that Ritchie is an evil God. He knows everything that is going on in his base at any given time, how to program and control machines, and how to get things done in a post-apocalyptic world. What else could you need? That's why, one day when he surprised me with a visit to my room, my first thought was that he knew all about my secret business with Noname.

"Hi, Teo. How's it going?" Ritchie asked. 
Quite well in fact; I've learned forbidden knowledge in the basement, made a deal with a machine controlled by you, and am desperately trying to leave this madhouse, I thought. 

"Hi, Ritchie! I'm fine, how are you?" I said. 
"Fine, thanks." he replied. "You have an opportunity to get a huge raise. You have a chance to move up to Wonderland." 
"Wonderland?" I asked, hoping it sounded like I had never heard the term.

"It's the biggest resistance base on Earth. The best human programmers are there." 
"Okay... but why me, Ritchie? You never seemed to like me much." 
"And I still don't. But current circumstances require one more person. To put you in that slot, I need to train you more."

 in C#." Ritchie began. 
In some tasks, you'll use values that never change. For example, the math constant Pi. Do you know the value?" 
"Sure, 3.14..." I answered, hoping that it sounded like I was trailing off to save time rather than because I didn't know the rest of the digits.

"3.14159265... and so on and so forth. The main thing to know for this lesson is that it never changes. A hundred years ago, and a hundred years in the future, it still will be the same number." 
"Got it." I said. 
"C# has a special keyword that lets us work with values like this: 

 with the declaration of a new value to indicate that the value never changes, like this:

"It looks just like a variable declaration." I said. 
"Yes," Ritchie replied, "it's almost the same thing. You just need to append the keyword, 

 , before the declaration. The difference is that 

you can never change the value that you declare with 

 ." he continued. "When the compiler sees a constant in your code, it replaces all usages of that constant with the actual value of the constant. Look here:" 

"Is this clear, Teo?" Ritchie asked. 
"Yes, I answered. " 

The compiler takes the value of the constant and writes it directly in every place where the constant is used 

"Very good, Teo. That's right. Knowing that, you probably can guess whether you can use variables in a constant declaration?" 
"I'd guess no," I said, "because variables don't exist when the compiler tries to calculate the constant value." 
"Bravo!" Ritchie said, sounding uncharacteristically pleased with me. Maybe it was because he realized he had found his tenth candidate for Wonderland. 

To sum it up: you can use constants to declare constants and variables, but you can't use variables to declare constants. 

"Ritchie," I asked, "what types can I use with 

 ?" 
"You can use all the types you've learned up to now, but not arrays. 

" 
"Thank you Ritchie." I said. "I think I've got the hang of what a 

"Two things to remember before we're done here." Ritchie said. "A 

"That's it Teo. Let's have you practice what you just learned. Head up to our virus production factory on the third floor and lend a hand."

Learn how to apply const keyword in C# for fields and locals to indicate that the value never changes. Examples and tasks.