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Data Type Size (in bytes) Range
-1.7976931348623157 × 10³⁰⁸ to
double 8
1.7976931348623157 × 10³⁰⁸
~ -1.189731495357231765 × 10⁴⁹³² to ~
long double 12
1.189731495357231765 × 10⁴⁹³²
Non-Primitive Data Types
Non-primitive data types are user-defined data types in C++ that are used to store multiple
values or create custom data structures. The table below shows the types, descriptions, and
examples of common non-primitive data types in C++:
Data Type Description Example
class Student {
A user-defined type that can hold both data and functions;
class int rollNo;
used in object-oriented programming.
};
struct Book {
A lightweight user-defined type to group different data string title; int
struct
types together. pages;
};
enum Day {
A user-defined type that assigns names to a set of integer
enum SUN, MON, TUE
constants.
};
union Data {
A user-defined type where all members share the same
union int x; float y;
memory location; only one value can be stored at a time.
};
Variables
Variables are memory locations used to store values. When a variable is created, a specific size
of memory space is allocated for it. This space is referred to by the name assigned to the variable,
which is called an identifier.
Naming Conventions for Variables
Following are the naming conventions used to declare a variable in C++:
A variable name must start with a letter (a–z, A–Z) or an underscore ( _ ).
A variable name cannot start with a digit (0-9).
Keywords cannot be used as variable names.
A variable can only contain alpha-numeric characters and underscore (A–Z both capital as
well as small) and (0–9) numbers.
No special symbols like ! , @ , #, $, %, etc. can be used in variable name.
Variable names are case sensitive, meaning myVar and MyVar are different.
Variable names cannot contain blank space.
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Touchpad MODULAR (Ver. 2.0)

