03 Variables

Variables

Bits: 0 or 1

All values are stored as groups of 0-1 bit values

Variable naming

Variable names can consist of: letters (any combination of uppercase/lowercase), numbers, underscore. Variable names are case sensitive. MyVariable is different from myVariable The following are NOT allowed:

• Variable names starting with a number
• Spaces, punctuation, math symbols

Scope

• Every variable needs a home. There are no global variables in C#.
• Variables are only valid within the code block where they are declared and any of it's contained code blocks.
• Variables are not valid above where they are declared within a code block.

Coming from Scratch

Document comparing scratch variables with C# variables

Value Types vs Reference Types

Value Data Types

Category	Common	Type	Bits	Range	Description
True/False	*	bool	8	true or false	Only one bit is used.
Whole Numbers		byte	8	0 - 255	Unsigned 8 bit number
		sbyte	8	-128 - 127	Signed 8 bit number
		short	16	-32,768 - 32,767	Signed 16 bit number
		ushort	16	0 - 65,535	Unsigned 16 bit number
	*	int	32	±2,147,483,648	Signed Whole numbers up to 2 billion.
		uint	32	0 - 4 billion	Unsigned whole numbers up to 4 billion.
		long	64	±9,223,372,036,854,775,807	Crazy big whole numbers.
		ulong	64	±18,446,744,073,709,551,615	Crazy big positive only whole numbers.
Fractional Numbers		decimal	128	±1x10-28 - ±8x1028	Used for money or where there are a fixed number of decimal places. Very precise, up to 29 significant digits.
	*	float	32	±3 x 1028	Not as accurate as double, but faster and half the memory. Often used in games.
		double	64	±2 x 10308	Much more accurate than float, but slower and twice as much memory. Rarely used in games.
Characters		char	8	Any one Ascii character	A single letter or symbol
Time		DateTime		Any time	Represents a date and time
Unity Specific	*	Vector2	2 * 32	Same as float	Stores a two dimensional x,y position or offset
	*	Vector3	3 * 32	Same as float	Stores a three dimensional x,y,z position or offset as 3 floats
	*	Quaternion	3 * 32	Same as float	Stores a three dimensional rotation

Reference Data Types

Category	Common	Type	Bits	Range	Description
Characters	*	string	(varies)	Ascii or Unicode characters	One or more symbols or words

Nullable (value type)

Any type can be made nullable. The nullable variable itself will be a value type (since it is a struct) even if the value it contains may be a reference type. In the variable declaration, appending a Question Mark ? character after the type converts the type to a nullable type.

int? myFirstInt = 1;    // Value is 1
int? myOtherInt = null; // Value is null (not 0)
int myBadInt = null;   // Error - not nullable

Enum (value type)

This is a custom type you can create to store a list of values. As far as the computer is concerned, these are just int numbers. The named values are to make the code easy to read and understand.

Arrays (reference type)

Lists

Structs

Tuples