Data Types In C++ | All 4 Categories Explained With Code Examples

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One of the fundamental concepts of any programming language is data types. What is that? In simple terms, it refers to the type of data stored in a variable. There are a wide variety of data types in C++ programming that are used for different purposes and intentions. This type not only determines the type of data but also the memory size/ space it takes. For example, the integer data type takes 4 bytes of space in memory. 

All the data types in C++ can be classified into 4 categories (or types): primitive/ built-in types, derived data types, user-defined types, and abstract data types. In this article, we will discuss the categories of data types in Cpp in detail, as well as their subtypes, with the help of code examples. 

What Are Primitive Data Types In C++?

Primitive data types, also referred to as built-in data types in C++, are ones that are predefined in a language. In this section, we will look at these common data types in C++ programming language (and their type sizes) that represent basic values, such as integers, characters, and floating-point numbers. We have explained all these basic types in detail, followed by a sample C++ program.

The Integer Data Type In C++

The int keyword represents the integer data type/ variable type that stores integral values without decimal values. The size of an integer type depends on the platform and generally varies between 2 bytes and 4 bytes of memory space. The range of values is (-)2,147,483,648 to 2,147,483,647.

Syntax: 

int myInteger = 42;

The Unsigned Integer Data Type In C++

This is similar to int, but the difference is that type unsigned can only represent non-negative numeric values without decimal places. The format specifier for this type of unsigned int is %u. It also takes up to 4 bytes of memory space and has a range of 0 to 4,294,967,295.

Syntax: 

unsigned int myUnsignedInteger = 123;

The Character Data Type (char) In C++

This fundamental type is represented by the keyword char. It refers to a single character data type/ alphabetical character value. When we initialize a variable with a char data type, we must enclose the respective characters in single quotes. The size of the char variable is typically 1 byte of memory space, and it can represent 256 different characters.

Syntax: 

char myChar = 'A';

The Unsigned Character Data Type In C++

This is similar to a single char, but the type unsigned only represents non-negative values. And it takes up 1 byte of memory space.

Syntax: 

unsigned char myUnsignedChar = 'X';

The Float Type/ Floating-Point Data Type In C++

The float data type refers to a floating-point value, i.e., a value that has a whole integer part with a single precision of approximately 6 decimal digits. A float variable data type generally occupies 4 bytes of space in memory.

Syntax: 

float myFloat = 3.14f;

The Double Data Type In C++

The type double represents a floating-point number with double precision of approximately 15 decimal digits. This can be considered an extension of the floating-point type and is hence also referred to as double floating or double-precision floating-point value. The size of this double variable is typically 8 bytes of memory space.

Syntax: 

double myDouble = 2.71828;

The Long Double Type In C++

The long double keyword represents a floating-point number with quadruple precision. The size of this data type is at least 8 bytes while going up to 16 bytes on certain systems and compilers.

Syntax: 

long double myLongDouble = 3.14159265358979323846L;

The Bool Type Data Type In C++

This data type represents a Boolean variable or boolean values, i.e., either true or false. In terms of numbers, a true equates to 1, and a false equates to 0. The size of a boolean data type is typically 1 byte.

Syntax: 

bool myBool = true;

The Long Data Type IN C++

Represents integer values that require more storage space than int data type (since it is longer). Typically its size is 4 bytes, but it can go up to 8 bytes depending on the system and compiler used.

Syntax: 

long myLong = 123456L;

The Unsigned Long Data Type In C++

This is similar to long, but the type unsigned can represent only non-negative values. It also takes 4 bytes of memory and can go to 8 bytes depending on the system and compiler used. It ranges from 0 to 4,294,967,295.

Syntax: 

unsigned long myUnsignedLong = 987654UL;

The Long Long Type In C++

This represents integer values that require more storage space than even the long int data type. It’s typically 8 bytes in size, and ranges from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807.

Syntax: 

long long myLongLong = 9223372036854775807LL;

The Unsigned Long Long Type In C++

This is similar to long long, with the type unsigned indicating only non-negative values. It takes up 8 bytes of memory and has a range of 0 to 18,446,744,073,709,551,615.

Syntax: 

unsigned long long myUnsignedLongLong = 18446744073709551615ULL;

The Short Data Type In C++

This represents integers that require less storage space than int (since it is shorter). It takes up to 2 bytes of memory and has a range of -32,768 to 32,767.

Syntax: 

short myShort = 32767;

The Unsigned Short Data Type In C++

This is similar to short, but it can represent only non-negative values as indicated by the unsigned keyword. It also takes up 2 bytes of memory while the range values are 0 to 65,535.

Syntax: 

unsigned short myUnsignedShort = 65535;

The Wide Character Type In C++

A wide character data type, represented by wchar_t notation, refers to characters that require more storage than the typical 8-bit (1 byte) char type, allowing for a larger set of characters to be represented. It typically takes 2 bytes of space but can go up to 4 bytes as well. 

It is essential for handling extended character sets that include characters from various languages and symbols beyond what the normal 8-bit data type (char) can represent.

The Void/ Empty Data Type In C++

The void data types are special types that represent the absence of a specific type. That is, the values stored in void type variables lack a particular type. They are mainly used as return types in functions (called void functions) and to declare pointers of type void.

Syntax: 

void myFunction() {
// Function with no return type
}

Example For Primitive Data Types In C++

These primitive or built-in datatypes can be used in combinations such as long double, short int, short double, etc. The simple C program below shows all these standard data types along with their sizes in C++.

Code Example:

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Output:

size of int(in bytes):4
size of unsigned int(in bytes):4
size of char(in bytes):1
size of unsigned char(in bytes):1
size of float(in bytes):4
size of double(in bytes):8
size of long double(in bytes):16
size of bool(in bytes):1
size of long(in bytes):8
size of unsigned long(in bytes):8
size of long long(in bytes):8
size of unsigned long long(in bytes):8
size of short(in bytes):2
size of unsigned short(in bytes):2

Explanation: 

We begin the C++ program example by including the <iostream> header file needed for input/ output operations and also declare the usage of namespace std.

1. Inside the main() function, we use a series of cout statements to print the sizes (in bytes) of different data types. 
2. The cout statements include a formatted string where the program fills in the sizes using the sizeof() operator. This operator returns the size in bytes of the specified data type.
3. The data types include int, unsigned int, char, unsigned char, float, double, long double, bool, long, unsigned long, long long, unsigned long long, short, and unsigned short.
4. The output of the program will display the sizes of each data type in bytes.

Derived Data Types In C++

The data types that are defined with the help of the fundamental data types (referred to as base types) are called derived data types. There are four derived data types in C++, namely arrays, pointers, function types, and references.

Function Types In C++

A function is a block of code that defines how to perform a specific task/ operation on the input values it takes. They provide a way to modularize code by grouping a set of instructions under a single name. We can then use a function to perform the specific task repeatedly, thus improving code organization, readability, and reusability.

Syntax: 

returnType functionName(parameterType1 parameterName1, parameterType2 parameterName2, ...) {
// Function body
return returnValue;} // Return statement (if applicable)

Here,

• The returnType refers to the data type of the return value, and the return keyword indicates that it is the return statement.
• The functionName refers to the identifier/ name of the function, and the curly braces contain the lines of code that make up its body.
• ParamterType1, paramterType2, and so on refer to the data type of the parameters the function takes and their names are given by parameterName.

Code Example: 

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Output:

Sum: 12

Explanation:

1. We begin the C code by declaring a function named addNumbers(). This function takes two integer parameters (a and b), calculates the sum of them, and returns the result.
2. Inside the main() function, we call the addNumbers() function with the values 5 and 7 as arguments.
3. This call invokes the function and stores the total/ sum in the variable result.
4. We then print the result to the console using the cout statement, as mentioned in the code comments.
5. The main() function terminates with a return 0 statement indicating successful completion.
6. Outside of the main(), we define the function, which uses the addition arithmetic operator to calculate the sum and return the same.

Also Read- Function Prototype In C++ | Definition, Purpose & More (+Examples)

C++ Array

An array is a collection of elements of the same data type stored in contiguous memory locations. The elements are accessed by their position, which is specified by an index value. IN an array data type, the index starts from 0, i.e., the 1st element is at index 0, and so on.

The size of an array is fixed at compile-time and can’t be changed during program execution. Array input and output are usually dealt with with the help of control statements.

Syntax: 

DataType arrayName[Size];

Here,

• DataType refers to the type of the values stored inside the array, which can be integers, characters, strings (interestingly, a string is an array of characters), etc.
• The arrayName refers to the name we give to the array, and the size refers to the number of elements inside the array.

Below is an example that shows the implementation of the array in a C++ program.

Code Example:

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Output:

1 2 3 4 5 6 7 8 9 10

Explanation: 

We begin the example C program above by including essential header files and indicating the usage of the namespace.

1. Inside the main() function, we declare an integer array arr of size 10, meaning it can store up to 10 integer values. 
2. Then, we create a for loop to initialize the array. The loop control variable i is initially set to 0, and loop continues iterations will it remains less than 10.
3. In every iteration, the loop accesses the array element at ith position and assigns a value i+1 to it. It then increments the value of the control variable 1 and continues iteration.
4. By the end of this loop, the array will be initialized with numbers from 1 to 10.
5. We use another for loop containing cout statements to traverse through the array and print its elements separated by white space. 

C++ - Pointer Data Type

A pointer is a derived data type that stores the memory address of another variable. It allows us to indirectly access a variable by manipulating the address stored in the pointer. They are often used for dynamic memory allocation at run-time and are instrumental in implementing abstract data types such as linked lists, trees, stacks, queues, etc.

Syntax: 

dataType* pointerName;

Here,

• dataType refers to the type of the variable whose location is being pointed to.
• The pointerName refers to the name we give to the pointer being declared.

Code Example:

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

Output:

The value of n: 10
The address of n: 0x7ffd775961bc
The value of ptr (address stored in it): 0x7ffd775961bc
The value of *ptr(value at the address stored in ptr): 10
The address of ptr: 0x7ffd775961c0
The size of ptr: 8

Explanation:

1. In the main() function of the example above, we first declare an integer variable n and initialize it with the value 10.
2. Next, we declare a pointer variable ptr and initialize it with the address of the integer variable n using the address of/ reference operator.
3. We then use a series of cout statements to print the following-
   • The value is stored in variable n and its address, which we get using the address-of operator.
   • Then, we print the value stored in pointer ptr (which is the address of n) and the data at the address stored in ptr (which is the value of n).
   • Similarly, we print the address of the ptr variable and the size of the pointer using the sizeof() operator. 
4. As shown in the output, the pointer variable ptr points to the data stored inside it, which in this case is n.

Also, read- Dynamic Memory Allocation In C++ Explained In Detail (With Examples)

User-Defined Data Types In C++

User-defined data types are the ones that a user creates using predefined or built-in data types, for their specific purpose. There are several ways to define custom data types in C++ that allow programmers to cater to more complex data types than those provided by primitive data types. This includes structures, unions, enumerations, classes, and typedef.

Enumerations Data Type In C++

Enumerations are user-defined data types that consist of a set of name constants or enumerators. They are often used to represent a set of related values that have a common meaning. In C++, they are defined using the enum keyword, and each value is assigned an integer by default. They are used to improve the readability and maintainability of the code.

Syntax: 

enum EnumName {
EnumValue1,
EnumValue2,
// ... additional values
};

Here,

• The enum keyword indicates that the data type of the variable is an enumeration.
• EnumName refers to the name of the variable, and EnumValue refers to the respective instances of the variable type/ values we assign to them.

Here is an example code that shows how enumerators work in C++.

Code Example:

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

Output:

0 1 2 3 4 5 6

Explanation: 

1. We define an enumeration (enum) named dayofweek inside the main() function. This enum variable represents the days of the week.
2. Next, we create 7 instances of the enum variable, one for each day of the week, i.e., day1, day2, so on, and assign values corresponding to the days.
3. Then, we use a series of cout statements to print the numeric values assigned to each day of the week using the enum instances.

Structures Data Types In C++

The C++ structures are user-defined data types that group together variables of different data types under a single name (or single type, since structure is also a type). They are often used to represent real-world entities that have multiple attributes. This way they help organize data and improve the readability, maintenance, and modularity of code.

Syntax: 

struct StructName {
dataType1 member1;
dataType2 member2;
// ... additional members
};

Here,

• The struct keyword indicates that we are defining a structure data type variable whose name is given by StructName.
• The dataType and member indicate the type of the data member and its name, respectively.

Look at the example below to understand how structures work in C++ programs.

Code Example:

I2luY2x1ZGU8aW9zdHJlYW0+CnVzaW5nIG5hbWVzcGFjZSBzdGQ7CgpzdHJ1Y3QgRW1wbG95ZWV7CmNoYXIgbmFtZVszMF07CmNoYXIgaGlyZWRhdGVbMzBdOwpmbG9hdCBzYWxhcnk7Cn07CgppbnQgbWFpbigpewpzdHJ1Y3QgRW1wbG95ZWUgZW1wPXsiU2hpdmkiLCIzMS8wNC8yMDI0Iiw4MDAwMC4wMH07CmNvdXQ8PCJUaGUgRW1wbG95ZWUgRGV0YWlscyBBcmUtIjw8ZW5kbDsKY291dDw8Ik5hbWUgb2YgZW1wbG95ZWU6Ijw8ZW1wLm5hbWU8PGVuZGw7CmNvdXQ8PCJIaXJpbmcgZGF0ZTogIjw8ZW1wLmhpcmVkYXRlPDxlbmRsOwpjb3V0PDwiU2FsYXJ5OiAiPDxlbXAuc2FsYXJ5PDxlbmRsOwp9

Output:

The Employee Details Are-
Name of employee:Shivi
Hiring date: 31/04/2024
Salary: 80000

Explanation:

1.  We begin by defining a structure called employee, which contains three data members/ components that represent the details of an employee. They are-
   
   • A character variable name to store the name of the employee, which can be up to 30 characters.
   • Another character variable hiredate to store the date of hiring of the employee, which has a size limit of 30 characters.
   • And a float-type variable salary to store the employee's salary.
2. Then, inside the main() function, we create an instance of the Employee struct called emp and initialize it with specific values. 
3. Finally, we use cout statements to print the details of the employee, including their name, hiring date, and salary, to the console.

Union Data Types In C++

Unions are user-defined data types that allow programmers to store different data types in the same memory location. This means that since they share the memory, you can access only one element/ member of the union at a given point in time. Also, the size of the union is dependent on the largest member attribute in terms of memory usage.

Syntax: 

union UnionName {
dataType1 member1;
dataType2 member2;
// ... additional members
};

Here,

• The union keyword indicates that we are defining a variable/ element of union data type whose name is given by UnionName.
• The terms member and dataType refer to the name of the data variable and its data type, respectively.

Below is an example that shows how unions are used in C++ programs.

Code Example:

I2luY2x1ZGU8aW9zdHJlYW0+CnVzaW5nIG5hbWVzcGFjZSBzdGQ7Cgp1bmlvbiBEYXRhewppbnQgaTsKZmxvYXQgZjsKZG91YmxlIGQ7Cn07CgppbnQgbWFpbigpewpEYXRhIHZhcjEsdmFyMix2YXIzOwp2YXIxLmk9MTA7CnZhcjIuZj0zLjE0Owp2YXIzLmQ9OC43NjgzNzsKCmNvdXQ8PCJJbnRlZ2VyIHZhbHVlOiI8PHZhcjEuaTw8ZW5kbDsKY291dDw8IkZsb2F0IHZhbHVlOiI8PHZhcjIuZjw8ZW5kbDsKY291dDw8IkRvdWJsZSB2YWx1ZToiPDx2YXIzLmQ8PGVuZGw7Cn0=

Output:

Integer value:10
Float value:3.14
Double value:8.76837

Explanation: 

We begin the sample C code by including the needed header file and using the namespace.

1. We define a union named Data to represent a collection of different data types (int, float, double) sharing the same memory location.
2. Then, inside the main() function, we declare 3 instances of the Data union, i.e., var1, var2, and var3.
3. Next, we initialize these members of the union with values 10, 3.14, and 8.76837. Since all members share the same memory, assigning a value to one member may affect the value of another member.
4. Finally, we use cout statements to print the values of the union members based on their respective data types.
5. This demonstrates the use of a union, where different types of data can be stored in the same memory location.

Classes In C++

These are not the traditional C++ data types per se. Instead, classes are user-defined data types that consist of data members (variables) and member functions (functions) that can be accessed through objects. Objects are instances of the class and are used to access the data members and member functions of the class.

The concept of classes and objects is of an integral part of object-oriented programming that forms the basis for other OOPs concepts like inheritance in C++.

Syntax: 

class ClassName {
private:
DataType1 member1;
//More data memebers
public:
ClassName();
//memberFunctions()

};

Here,

• The class keyword indicates we are defining a class with the name ClassName.
• Next, the terms private and public are the access specifiers that control the accessibility of class members, i.e., who and from where can access the respective data members.
• The className() is the default class constructor which initializes the data members.
• The term memberFunction() refers to the functions/ methods that are a part of the class. 

Below is an example to show how classes and objects work in C++.

Code Example:

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Output:

Area of square of side 5 is 25

Explanation:

1. We define a class named Square encapsulating data members (side of integer type) and a member function (area) that calculates and returns the square of the side.
2. Then, in the main() function, we create an object s of the Square class and then use the dot operator to initialize the side data member with the value of 5.
3. We then use a cout statement to print the area of the square by calling the area() function on the side variable.

Also Read- OOPs Concept In C++ | A Detailed Guide With Codes & Explanations

Typedef Data Types In C++

In C++, the typedef keyword is used to create an alias (alternate name) for existing data types. This can make code more readable and manageable, especially when dealing with complex or lengthy type declarations. The typedef keyword simplifies the process of defining custom names for various data types.

Here's the general syntax for using typedef:

typedef existing_type new_type_name;

Below is an example to illustrate the usage of typedef in C++.

Code Example:

I2luY2x1ZGU8aW9zdHJlYW0+CnVzaW5nIG5hbWVzcGFjZSBzdGQ7CgovLyBPcmlnaW5hbCB0eXBlIGRlY2xhcmF0aW9uCnR5cGVkZWYgaW50IEludGVnZXI7CgppbnQgbWFpbigpIHsKLy8gVXNpbmcgdGhlIHR5cGVkZWYgYWxpYXMKSW50ZWdlciBteU51bWJlciA9IDQyOwoKLy8gT3JpZ2luYWwgdHlwZSB1c2FnZQppbnQgYW5vdGhlck51bWJlciA9IDI0OwoKY291dCA8PCAiVXNpbmcgdHlwZWRlZjogIiA8PCBteU51bWJlciA8PCBlbmRsOwpjb3V0IDw8ICJXaXRob3V0IHR5cGVkZWY6ICIgPDwgYW5vdGhlck51bWJlciA8PCBlbmRsOwoKcmV0dXJuIDA7Cn0=

Output: 

Using typedef: 42
Without typedef: 24

Explanation:

1. We begin by declaring a new data type by using the typedef keyword. 
2. Integer becomes an alias for the existing type int.
3. In the main() function, we declare a variable myNumber using the Integer alias.
4. Then, we declare another variable, anotherNumber, using the original type int.
5. Both variables, myNumber and anotherNumber, are essentially of the same type (int).
6. The cout statements print the values of the two reference variables, demonstrating the use of typedef for code readability.
7. The return 0 statement indicates successful program execution.

Abstract Data Types In C++

Abstract data types are defined by their behaviour rather than their implementation because they are not data types in the traditional sense but data structures. In other words, they are used to represent complex data structures such as linked lists, stacks, queues, and trees. Programmers define their own data types with specific behaviour and individual characters. Listed below are some of the most used abstract data types in C++.

Linked List In C++

It’s a data structure in which elements are stored in a sequence, and each element points to the next. The first element is called the head, and the last element points to null. Linked lists are useful for dynamic data structures where the size is not known beforehand.

Syntax:

struct Node {
int data;
Node* next;
};
class LinkedList {
private:
Node* head;
public:
LinkedList();
void insertFront(int value);
void display();
};

Here’s an example of the implementation of a linked list in C++.

Code Example:

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

Output:

1 2 3

Explanation:

1. We begin by defining a structure named Node that represents a node in a linked list. Each node contains an integer data value and a pointer next to the next node in the list.
2. Next, we define a function printlist that takes a pointer to the head of a linked list as a parameter and prints the elements of the list using a while loop.
3. In the main() function, we declare three nodes (head, second, and third) using the Node structure. Memory is allocated for each node using the new keyword.
4. We then assign values and pointers to each node to create a simple linked list: 1 -> 2 -> 3 -> NULL.
5. Then, we call the printlist() function with the head of the list as an argument to print the elements of the linked list.

Stacks Data Types In C++

This is a data structure where elements are stacked one on top of the other. They follow a last-in-first-out (LIFO) order, meaning, its elements are inserted and removed from the top end. Stacks are useful in situations where the most recently added element is the most important. For example, function calls are stored in a call stack and popped off the stack after the function returns control.

Syntax:

#include<stack>
int main() {
std::stack<int> myStack;
myStack.push(1);
myStack.pop();
return 0;
}

Here’s an example of a basic implementation of a stack.

Code Example:

I2luY2x1ZGU8aW9zdHJlYW0+CiNpbmNsdWRlPHN0YWNrPgp1c2luZyBuYW1lc3BhY2Ugc3RkOwoKaW50IG1haW4oKXsKc3RhY2s8aW50PnM7CnMucHVzaCgxKTsKcy5wdXNoKDIpOwpzLnB1c2goMyk7Cgp3aGlsZSghcy5lbXB0eSgpKXsKY291dDw8cy50b3AoKTw8ZW5kbDsKcy5wb3AoKTt9Cn0=

Output:

3
2
1

Explanation: 

1. In the main() function, we declare a stack of integers named s using the stack template class.
2. We then use the push() function to push the values 1, 2, and 3 onto the top of the stack.
3. Next, we create a while loop to iterate through the elements in the stack. It first checks if the stack is not empty using the logical NOT operator and the empty() function.
4. If the condition is false, i.e., the stack is not empty, the loop prints the top element using the cout statement and removes it from the stack using the pop() function. 
5. If the condition is true, i.e., the stack is empty, then the loop terminates.

Queues Data Types In C++

It is a linear data structure that follows a first-in-first-out (FIFO) order, where elements are inserted at the rear end and elements are removed from the front end. Queues are useful in situations where a group of elements need to be processed in the order they were received.

Syntax: 

#include<queue>
int main() {
std::queue<int> myQueue;
myQueue.push(1);
myQueue.pop();
return 0;
}

Here’s an example of how queues work in C++.

Code Example:

I2luY2x1ZGU8aW9zdHJlYW0+CiNpbmNsdWRlPHF1ZXVlPgp1c2luZyBuYW1lc3BhY2Ugc3RkOwoKaW50IG1haW4oKXsKcXVldWU8aW50PnE7CnEucHVzaCgxKTsKcS5wdXNoKDIpOwpxLnB1c2goMyk7Cgp3aGlsZSghcS5lbXB0eSgpKXsKY291dDw8cS5mcm9udCgpPDxlbmRsOwpxLnBvcCgpOwp9Cn0=

Output:

1
2
3

Explanation:

1. The code includes two header files: <iostream> for input and output operations and <queue> for using the queue data structure.
2. In the main() function, we declare a queue of integers named q using the queue template class.
3. We then use the push() function to push the values 1, 2, and 3 onto the back of the queue.
4. Next, we create a while loop to iterate through the elements in the queue as long as it is not empty (i.e., !q.empty()).
5. Inside the loop, the front element of the queue is printed using cout statements.
6. After that, we use the pop() method to remove the front element from the queue.
7. The loop continues until the queue becomes empty, printing the front element at each iteration.

Trees Data Structure/ Data Type In C++

It is a data structure that consists of nodes connected by edges. Each node can have multiple child nodes, except for the leaf nodes, which have no children. Trees are useful in situations where hierarchical relationships need to be represented.

Syntax: 

struct TreeNode {
int data;
TreeNode* left;
TreeNode* right;
};
TreeNode* createSampleTree();
int main() {
TreeNode* myTree = createSampleTree();
return 0;
}

Given below is an implementation of the tree in C++.

Code Example:

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

Output:

1
2
3

Explanation: 

1. We define a structure named Node representing a node in a binary tree. Each node contains an integer data value and pointers to its left and right children.
2. Next, we define a recursive function, printTree, that traverses a binary tree in a pre-order fashion and prints the data of each node.
3. In the main() function, we create a simple binary tree with three nodes, i.e., root, left child, and right child.
4. Next, we assign integer values to each node in the tree (1 for the root, 2 for the left child, and 3 for the right child).
5. Then, we call the printTree function to traverse and print the binary tree in pre-order.

Data Type Modifiers In C++

In C++, data type modifiers are keywords that modify the properties of basic data types or fine-tune the characteristics to better suit the requirements of your program. Here are some commonly used data type modifiers in C++:

• Signed: This is the default modifier for integer types. It allows both positive and negative values. E.g., signed int temperature = -10.
• Unsigned: This modifier is used when only non-negative values are needed. It effectively doubles the positive range. E.g., unsigned int count = 100.
• Short: It reduces the size of an integer, allocating less memory. It is typically used when memory efficiency is crucial. E.g., short int smallNumber = 32767.
• Long: It increases the size of an integer, providing a larger range of values. E.g., long int bigNumber = 1234567890.
• Float: Represents single-precision floating-point numbers. E.g., float myFloat = 3.14159f.
• Double: Represents double-precision floating-point numbers (larger range and precision compared to float). E.g., double myDouble = 3.14159265358979.
• Long Double: Represents extended precision floating-point numbers. E.g., long double myLongDouble = 3.14159265358979323846L.

Declaring Variables With Auto Keyword

In C++, the auto keyword is used for type inference, allowing the compiler to automatically deduce the data type of a variable based on its initializer. This feature was introduced in C++11 and is part of modern C++ programming. Using auto can simplify code, especially when dealing with complex or lengthy type names.

The Syntax to Declare Variables Using the auto Keyword:

auto variable_name = initial_value;

Here, as must have noticed we have used the auto keyword instead of the data type. This signals the compiler to look at the initial_value and on basis of that decide/ assign the data type of the variable known as variable_name.

Code Example:

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Output: 

x: 42
First element: 1
Sum: 8

Explanation:

We begin by including the header file for input and output operations: #include<iostream> and the <vector> header for using the vector container.

1. Inside the main() function, we then declare a variable x with the auto keyword and initialize it with the value 42. The compiler deduces that x is of type int.
2. Next, we declare an integer vector called numbers and initialize it.
3. Then, we declare a variable iterator and initialize it with the iterator pointing to the beginning of a vector. The compiler deduces that the iterator is of type vector.
4. We then declare a variable add and initialize it with the lambda() function, i.e., auto add = [](int a, int b) { return a + b; }. The compiler deduces the type of add based on the lambda function's signature.
5. Lastly, we use cout statements to print the values of x, the first element of the vector, and the result of the lambda function.

Conclusion

C++ offers a wide range of data types to choose from, including primitive, derived, user-defined, and abstract data types. It also provides data type modifiers to specify additional constraints about the behaviour of variables and pointers in C++ programs. Understanding the various data types in C++ and their uses is crucial for effective and efficient programming. Selecting the appropriate data type for a given problem can help optimize the code for both memory usage and runtime efficiency. A solid understanding of data types in C++ is an essential component of becoming a proficient C++ programmer.

Also read- 51 C++ Interview Questions For Freshers & Experienced (With Answers)

Frequently Asked Questions

Q. What is the difference between primitive and derived data types in C++?

Primitive data types are the fundamental data types in C++, such as int, char, float, double, bool, etc. In comparison, derived data types are built on top of primitive data types, such as arrays and pointers.

Q. What are abstract data types in C++?

Abstract data types (ADT) are data types that are defined on the basis of the behavior they exhibit and not on the basis of their implementation. ADTs don't specify the implementation of the data structure but rather the actions performed on it. Examples of abstract data types in C++ are linked lists, trees, stacks, and queues.

Q. What is the size of integer data types in C++?

The correct size of an integer data type in C++ varies depending on the compiler and architecture being used. They vary from 4 bytes to 8 bytes. However, in general, they are 4 bytes.

Q. What is the difference between signed and unsigned data types in C++?

Signed data types can hold both positive and negative values, so their C++ range is from -2147483648 to 2147483647. In comparison, unsigned data types can only hold non-negative values, and their range is from 0 to 4294967295.

Q. What are user-defined data types in C++?

User-defined data types are custom-defined data types implemented by the programmer to create more complex data structures than those provided by primitive data types, such as structures, classes, enumerations, and unions. They are created using one or more primitive data types.

Q. What are pointers in C++?

A pointer is a derived data type that stores the memory address of another variable. It allows us to indirectly access a variable by manipulating the address stored in the pointer. They are often used to dynamically allocate memory at run-time and are instrumental in implementing abstract data types such as linked lists, trees, stacks, queues, etc.

Q. What are classes in C++?

Classes are user-defined data types that contain data members and member functions that operate on the data members. Objects are instances of a class and are used to access the data members and member functions of the class.

Q. What are data type modifiers in C++?

Data type modifiers are used to modify the behavior or properties of the basic data types in C++. The C++ language provides data type modifiers to specify additional constraints about the behavior of variables and pointers in C++ programs.

Q. What is the difference between a stack and a queue in C++?

Stacks are last in, first out(LIFO) data structures, while queues are first in, first out(FIFO) data structures. Stacks are used for expression evaluation and function call management. Queues are used for tasks like process scheduling and data buffering.

Q. What is the importance of data types in C++?

There are a wide range of data types to choose from, including primitive, derived, user-defined, and abstract data types. It is important for one to understand these different data types in C++ and to write effective and efficient code. 

You might also be interested in reading the following:

1. The 'this' Pointer In C++ | Declaration, Constness, Applications & More!
2. C++ Type Conversion & Type Casting Demystified (With Examples)
3. Storage Classes In C++ & Its Types Explained (With Examples)
4. Pointer To Object In C++ | Simplified Explanation & Examples!
5. Array Of Objects In C++ | A Complete Guide To Creation (Using Examples)