Primitive Data Types

Every variable in C# needs a type, and the built-in primitive types are the most basic kinds of data a variable can hold. Primitives store a simple value directly, which makes them fast and memory-efficient — unlike the string type you will meet soon, which is a reference type.

int quantity = 10;
double price = 4.99;
bool inStock = true;
char grade = 'A';

int stores whole numbers (no decimal point) and is the default choice for counting things. double stores decimal numbers and is the default choice for anything with a fractional part, like prices or measurements. bool can only ever be true or false, which makes it perfect for yes/no conditions — note that C# spells it bool, not boolean. char stores exactly one character, written in single quotes like 'A' — never double quotes, which are reserved for strings.

To store a single character like 'A', you use the ____ type.

C# also has smaller and larger whole-number types for when int isn't the right fit: byte and short save memory for tiny numbers, while long is used for whole numbers bigger than int can hold — you mark a long literal with an L at the end. For money and other values needing exact decimal precision, C# offers decimal, marked with an m suffix; it is more precise than double but slightly slower to calculate with.

long population = 8_000_000_000L;
byte smallNumber = 120;
decimal price = 19.99m;

Fields that belong to a class automatically get a default value if you don't initialize them — 0 for numeric types, false for bool, and a null character for char. Local variables declared inside a method, however, do not get a default value: the compiler forces you to assign one before you can use the variable, which helps catch bugs early.

A local variable declared inside a method automatically gets a default value, like 0, if you never initialize it.

Which primitive type would you use to store whether a light switch is on or off?