C++ - Derived Data Types

Derived Data Types in C++

Introduction

In C++, derived data types are types that are based on the fundamental or built-in data types. These types allow you to create more complex data structures. Derived data types include arrays, pointers, references, and functions. These types are widely used to build more complex data structures and manage data efficiently.

1. Arrays

An array is a collection of elements of the same data type stored in contiguous memory locations. The size of an array is fixed at the time of its creation, and it can store multiple values of the same type.

Array Syntax

type arrayName[arraySize];

Example

int numbers[5] = {1, 2, 3, 4, 5};

Array Access

Each element in an array can be accessed using its index, with indexing starting from 0.

cout << numbers[2];  // Outputs 3

Array Types

• Single-Dimensional Array: An array with only one set of indices (e.g., int arr[5];).
• Multi-Dimensional Array: An array with more than one index (e.g., a 2D array like int matrix[3][3];).

2. Pointers

A pointer is a variable that stores the memory address of another variable. Pointers are powerful tools in C++ for dynamic memory allocation and direct memory manipulation.

Pointer Syntax

type* pointerName;

Example

int num = 10;
int* ptr = #  // & gives the address of num

Dereferencing a Pointer

Dereferencing a pointer means accessing the value stored at the address the pointer is pointing to.

cout << *ptr;  // Outputs 10

Pointer Types

• Null Pointer: A pointer that doesn't point to any valid memory location. It is represented as nullptr in C++11 and later.
• Void Pointer: A generic pointer that can point to any data type. It is written as void*.

3. References

A reference is an alias for another variable. Unlike pointers, references cannot be reassigned to reference a different variable once they are initialized.

Reference Syntax

type& referenceName = originalVariable;

Example

int num = 20;
int& ref = num;  // ref is a reference to num

Reference Behavior

Changes made to the reference will also affect the original variable, as both refer to the same memory location.

ref = 30;
cout << num;  // Outputs 30

Reference Types

• Function References: References can be used to pass arguments to functions, allowing modifications to the original variables.

4. Function Types

A function in C++ can be considered a derived data type when it is treated as a pointer to a function. Functions have their own types based on the return type and the parameter types they accept.

Function Pointer Syntax

returnType (*functionName)(parameterTypes);

Example

int add(int a, int b) { return a + b; }
int (*funcPtr)(int, int) = add;

Function Pointer Usage

You can call a function through a pointer by using the dereference operator.

cout << funcPtr(5, 10);  // Outputs 15

5. Enumerations

An enumeration (enum) is a user-defined data type consisting of a set of named integer constants. It helps make the code more readable by using names instead of raw integer values.

Enum Syntax

enum EnumName { CONSTANT1, CONSTANT2, CONSTANT3 };

Example

enum Day { Monday, Tuesday, Wednesday, Thursday, Friday };  
Day today = Wednesday;

Enum Values

By default, the first constant is assigned the value 0, and the subsequent constants increment by 1. You can manually assign values to constants as well.

enum Day { Monday = 1, Tuesday, Wednesday, Thursday, Friday };  // Monday = 1, Tuesday = 2, etc.

Derived data types in C++ allow you to create more complex structures and manage data effectively. By understanding and using arrays, pointers, references, function types, and enumerations, you can write more efficient and powerful C++ programs.