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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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