Basics

Entry point

C#'s Entry point, like other languages is the Main function. It's the function that gets ran first whenever we start the program. For now there's no need to worry about static, void or string[], it's unimportant.

Take a look at the picture below, this is what a typical C# program looks like at first:

Data types

Variables are a container for us to store a value that belongs to a data type. There's two different types of value types: value and reference.

If you want to know more: - Value types store the actual value directly. - Reference types store a reference (memory address) that points to the value.

We can use built-in types that are defined by the language or build these data types ourselves. Sone of these types like the user-defined reference types will seem complicated at first, know that they're unimportant for now.

Value types

Predefined:

Real-word type	According C# keyword	Example
Whole numbers	int	-5 or 5
Floating point numbers	float or double	-5.5 or 5.5
Letters	char	'A' or 'z'
Validity	bool	true or false

User-Defined:

Real-word type	According C# keyword	Example
A lightweight type for grouping others.	struct	struct Point { public int X, Y; }
A set of names constant values.	enum	enum Days { Monday, Tuesday }

Reference types

Predefined:

Real-word type	According C# keyword	Example
Sentences (collection of letters)	string	"Hello World!"
A 'thing', any thing.	object	"Hello World!" or 5.5

User-Defined:

Real-word type	According C# keyword	Example
A constructed object that can do things.	class	class Dog{}
A contract / rules for objects on how to behave.	interface	interface Dog{}
A reference to a function.	delegate	public delegate int PerformCalculation(int x, int y);

Variables

Wokring with variables throughout our program we will often change their values. However, we also somewhat keep track of their state.

A variable can be declared without a initial value: int a;

Note that some types will get defaulted to a initial value like 0.

A variable can be assigned a value: a = 5;

A variable can be initialized (declared with a value): int a = 5;

Operators

We can perform some calculations or variables or literal values using operators.

There's a bunch of types of operators. Usually when thinking of operators we think of Arithmetic operators like plus.

For example: int a = 5 + 5; or int b = a + 5; or int c = a + b;

Arithmetic

Name	Operator
Addition	+
Subtraction	-
Multiplication	*
Division	/
Modulus	%
Increment	++
Decrement	--

Assignment

Name	Operator
Assignment	=
Addition assignment	+=
Subtraction assignment	-=
Multiplication assignment	*=
Division assignment	/=
Modulus assignment	%=

Comparison

Name	Operator
Equal to	==
Not equal to	!=
Greater than	>
Less than	<
Greater than or equal to	>=
Less than or equal to	<=

Logical

Name	Operator
Logical AND	&&
Logical OR	\|\|
Logical NOT	!