C++ Tutorial index

C++ Tutorial C++ History C++ installation C++ First Program C++ cin and cout C++ Data type C++ Variable C++ operator C++ Keywords C++ OOPS Concepts C++ Comments C++ Data Abstraction C++ Identifier C++ Memory Management C++ Storage Classes C++ Void Pointer C++ Array to function C++ Expressions C++ Features C++ Interfaces C++ Encapsulation

C++ Control Statements

C++ If C++ Nested if C++ If-else C++ If-else-if C++ Switch C++ Break C++ Continue C++ Goto C++ for loop C++ While loop C++ Do while loop

C++ functions

function in C++ C++ Call by Value C++ Call by Reference C++ Recursion function C++ inline function C++ Friend function C++ Friend functions function Pointer in C++ Sizeof() Operators in C++ C++ Math functions swap() function in C++ rand() and srand() in C / C++ wcscpy(), wcslen(), wcscmp() functions in C++ sort() function in C++ C++ vardiac() function System() function in C++ Fread function in C++ Programming Fscanf function in The C++ Gmtime function in C/C++ abs() function in C++ Sleep function in C++ Stoi function in C++ String erase() in C++ String Trim in C++ isprint() function in c++ is_trivial function in C++ div() function in C++ Set insert function in C++ rint(), rintf(), rintl() in C++ String append() function in C++ String push_back() in C++ String replace() in C++ Transform function in C++ exit() and _Exit() in C and C++ Std partition_point in C++ unique() in C++ ctime() function in C++ Gets() and Puts() in C++ Hypot(), hypotf() and hypotl() in C++ Log function in C++ Nearbyint() function in C++ setf() function in C++ Fill Function in C++ Map Find Function in C++ Malloc and Calloc in C++ Operator Function in C++ cin.get() in C++ seekp() Function in C++ eof() Function in C++ Emplace Back in C++ C++ macro function C_str in C++ Clock() in C/C++ round() function in C++ scalbn() function in C++ Stable Sort function in C++ Rotate in C++ Std:: Sort_heap in C++ Std::includes() in C++ STL std::memset() function in C++ Wcscmp() function in C++ Static Member function in C++ atof() function in C++ C++ Sin() function with Example cin.ignore() function in C++ Member function in C++ Pop_front Vector in C++ Vector resize() in C++ Malloc() and new in C++ std::distance in C++ C++ Date and Time fork() in C++ std::min in C++ isprint() in C++ rdbuf() in C++ fixed() Function in C++ setw() in C++ seekg() Function in C++ isdigit() Function in C++

C++ Function Miscellaneous

Precision of floating point numbers Using these functions floor(), ceil(), trunc(), round() and setprecision() in C++ function overloading in C++ Add two numbers using the function in C++ Advantage and disadvantage friend function C++ ATM machine program in C++ using functions Returning Multiple Values from a function using Tuple and Pair in C++ Find the Size of Array in C/C++ without using sizeof() function Pure Virtual function in C++ With Example Program Returning a function Pointer from a function in C/C++ Passing a Vector to a function in C++ functions in C++ With Types and Examples C++ Macro function Example Using Default Arguments with Virtual functions Virtual functions and Runtime Polymorphism Fesetround() and Fegetround() in C++ and their application Object as function Argument in C++ Private Member function in C++ Function Overriding in C++ C++ Program for Addition of Two Numbers Using functions function Object in C++ Elements of User Defined function in C++ Inline Functions in C++ Virtual Function in C++

C++ Arrays

Single dimension array Two dimension array

C++ Strings

C++ Strings

C++ Inheritance

C++ inheritance Single level inheritance Multilevel inheritance Multiple inheritance Hierarchical inheritance Hybrid inheritance

C++ Polymorphism

C++ Polymorphism C++ Overloading C++ Overriding C++ Virtual function

C++ Pointers

C++ Pointers C++ this pointer

C++ Exception Handling

C++ Exception Handling

C++ Constructors

C++ Constructors Default Constructor Parameterize Constructor Copy constructor Constructor Overloading Destructor

C++ File Handling

C++ File Handling C++ Writing to file C++ Reading file C++ Close file

C++ Programs

Structure of C++ Program Hello World Program in C++ C++ Program to Implement Shell Sort C++ Program to Implement Merge Sort C++ program to read string using cin.getline() C ++ Program: Alphabet Triangle and Number Triangle C++ Program: Matrix Multiplication C++ Program to Print Fibonacci Triangle C++ Program to find the product array puzzle C++ Program To Find Largest Subarray With 0 Sum C++ Program To Move All Zeros To The End of The Array C++ Program to find the element that occurs once C++ Program to find the largest number formed from an array Palindrome Number Program in C++ LCM Program in C++ Armstrong Number Program in C++ Factorial Program in C++ C++ Prime number program Program to convert infix to postfix expression in C++ Programs to Print Pyramid Patterns in C++ Array program in C++ Pattern programs in C++ Leap Year Program in C++ C++ Program for FCFS Depth First Search Program to Traverse a Graph in C++ inheritance Program in C++ Program that produces different results in C and C++ Example Program in C++ for input and Output Calculator Program using Switch in C++ Program for COPY Constructor in C++ Bank Program in C++ Anagram Program in C++

C++ Operators

Unary Operators in C++ Delete Operator in C++ C++ Bitwise XOR Operator Binary Operator Overloading in C++ Scope Resolution Operator in C++ C++ Ternary Operator New Operator in C++ Overloading array index operator in C++ Operator overloading in C++ Operators that cannot be overloaded in C++ Default Assignment Operator and References in C++ Conversion Operator in C++ Unary Operator Overloading in C++ Benefits of Operator Overloading in C++ Assignment Operator Overloading in C++ New and Delete Operator in C++ Insertion Operator in C++ Increment Operator in C++ Bitwise Operator in C++

C++ Examples

C++ Programming Examples While Loop Examples in C++ for Loop Examples in C++ Do-While Loop Examples in C++ SDL library in C++ with Examples C++ tcp client server example C++ tcp server example TCP Client Server Example in C++ Example of Parameterized Constructor in C++ Example of User Defined Data Type in C++

C++ Differences

C Vs C++ free() vs delete() in C++ Constructor Vs Destructor Passing by Reference Vs. Passing by the pointer in C++ C++ vs C# Structure Vs Class in C++ Virtual function Vs Pure Virtual function Structure Vs Class in C++ Exception Handling in C++ vs Java Static keyword in C++ vs Java inheritance in C++ vs Java C++ 11 vs C++ 14 vs C++ 17 Templates in C++ vs Generics in Java Bitwise Operator vs Logical Operator Type difference of Character literals in C VS C++ Copy Constructor vs Assignment Operator in C++ Map vs unordered_map in C++ Differences between #define & const in C/C++ Differences Between C Structures and C++ Structures Difference between Two Sets in C++ Difference between Exit and Return Differences between Local and Global Variable Difference between OOP and POP in C++ Difference between exit() and _Exit() in C++ Difference between int main() and int main(void) in C/C++ Difference Between Overloading and Overriding in C++ std::set_symmetric_difference in C++ Difference between Private and Protected in C++ Difference Between Encapsulation and Abstraction in C++ Difference between Template and Macro in C++ Difference between Abstraction and Interface in C++ Differences Between C++ and Javascript

How To

How to concatenate two strings in C++ How to Reverse a String in C++ using Do-While Loop How to Reverse a String in C++ using for Loop How to Reverse a String in C++ using While Loop How to create a table in C++ How to Setup Environment for C++ Programming on Mac How to call a void function in C++ How to create a directory or folder in C/C++ How to create a library in C++ How to create a stack in C++ How to create the Processes with fork in C++ How to Handle Divide by Zero Exception in C++ How to Declare Unordered Sets in C++ How to Sort an Array in C++ How to run program in turbo c++ How to Use Getline in C++ How is Multiset Implemented in C++ How to Build a Program in C++ How to Declare a 2d Array Dynamically in C++ How to create a button in C++ How the value is passed in C++ How to calculate size of string in C++ How to convert binary string to int in C++ How to convert string to float in C++ How to remove space from string in C++ How to use pair in C++ How to use the string find() in C++ How to Remove an Element From an Array in C++ How to Take Space Separated input in C++ How to Copy in Turbo C++ How to Use Pow in C++ How to Use Set in C++ How to Create Singleton Class in C++ How to Allocate Memory Dynamically in C++ How to Close Turbo C++ in Windows 10 How to Use Modulus in C++

C++ Questions

What does Buffer Flush mean in C++ What is endl in C++ What is Unary Operator Overloading in C++ Which operators cannot be overloaded in C++ What is Static Member function in C++ What is This Pointer in C++ What is Upcasting in C++ What Kind of Exceptions Are Available in C++ What is Memory Allocation for Objects in C++ What is a Linked List in C++ is assignment operator inherited in C++ When should we write own Assignment operator in C++ What is an Object in C++ What is Copy Constructor in C++ What is a Static Member Function in C++

C++ Interview Questions

Advanced C++ interview Questions Oops Interview Questions in C++


External merge sort in C++ Remove duplicates from sorted array in C++ C++ References C++ Mutable keyword initialize Array of objects with parameterized constructors in C++ Storage Classes in C goto statement in C and C++ C++ String Concatenation Heap Sort in C++ Swap numbers in C++ input Iterators in C++ Fibonacci Series in C++ Stack in C++ Maps in C++ Queue in C++ C++ Bitset C++ Algorithms Priority Queue in C++ C++ Multimap C++ Deque C++ array of Pointers Timsort Implementation Using C++ CPP Templates C++ Aggregation C++ Enumeration C++ Object Class C++ Queue initialize Vector in C++ Vector in C++ C++ STL Components C++ Maximum index Problem C++ find missing in the second array C++ Namespaces C++ OOPs Concept C++ Static C++ Structs C++ Try-Catch C++ User Defined Exceptions C++ Virtual Destructor Snake Code in C++ Splitting a string in C++ C++ Bidirectional Iterators C++ forward Iterators C++ Iterators C++ Output Iterators C++ Range-based for Loop Converting string into integer in C++ Type conversion in C++ Binary to Decimal in C++ Bit Manipulation in C++ C++ Constructor C++ Dijkstra Algorithm Using the Priority Queue C++ int into String C++ Signal Handling Decimal to Binary in C++ Decimal to Hexadecimal in C++ Decimal to Octal in C++ Hexadecimal to Decimal in C++ Octal to Decimal in C++ Reverse a Number in C++ C++ forward Iterators C++ Output Iterators Char Array to String in C++ Constructor Overloading in C++ Default arguments in C++ Different Ways to Compare Strings in C++ Dynamic Binding in C++ SET Data Structure in C++ Upcasting and Downcasting in C++ Reverse an Array in C++ Fast input and Output in C++ Copy elision in C++ Array of sets in C++ Binary Search in C++ Implementing the sets without C++ STL containers Smart pointers in C++ Types of polymorphism in C++ Const Keyword in C++ Type Casting in C++ Stringstream in C++ and its applications C++ Scope of Variables Star pattern in C++ using for Loops Top 5 IDEs for C++ That You Should Try Once Assertions in C/C++ C++ Convert int to String Continue in C++ While loop Diamond Pattern in C++ using for Loop infinite loop in C++ Loops in C++ Auto keyword in C++ C++ STL (Standard Template Library) Divide by Zero Exception in C++ Dynamic Constructor in C++ Dynamic Memory Allocation in C++ Floating Point Operations and Associativity in C, C++ and Java Implementation of a Falling Matrix in C++ Message Passing in C++ Pointer to Object in C++ Ways to Copy a Vector in C++ Structure Sorting (By Multiple Rules) in C++ Similarities between C++ and Java C++ Tricks for Competitive Programming Desired Capabilities in Selenium Web Driver in C++ Socket Programming in C++ Template Specialization in C++ Classes and Objects in C++ Convex hull Algorithm in C++ DES in C++ Structured Binding in C++ Functors in C++ Lambda Expression in C++ Roadmap to C++ Programming Substring in C++ Virtual base class in C++ Bits stdc++.h in C++ Top 14 Best Free C++ IDE (Editor & Compiler) for Windows in 2022 Bitmasking in C++ Features of OOPS in C++ Hospital Management Project in C++ include Guards in C++ Iostream in C++ Method overriding in C++ Naming Convention in C++ Nullptr in C++ Object Slicing in C++ Principles of Object-Oriented Programming in C++ Processing strings using std string stream in C++ Random Number Generator in C++ Singleton Design Pattern in C++ Size_t Data Type in C++ Skyline Problem in C++ Web Development in C++ Data Hiding in C++ Hashing in C++ Object in C++ Sum of all Elements between k1’th and k2’th Smallest Elements Virtual class in C++ Vector Size in C++ Top best IDEs for C/C++ Developers in 2022 Tensorflow in C++ Sliding Window Technique in C++ Reverse String Word-Wise in C++ RTTI in C++ Pthreads or POSIX Threads in C++ Reserved Keywords in C++ 10 Best C and C++ Books for Beginners & Advanced Programmers Add two numbers represented by two arrays in C++ Array of Object in C++ Containership in C++ Counting Frequencies of Array Elements in C++ Decltype type Specifier in C++ Dynamic _Cast in C++ Features and Use of Pointers in C/C++ int Max and int Min in C/C++ is It Fine to Write Void Main Or Main in C/C++ Compile Time Polymorphism in C++ Division in C++ Factorial of a Number in C++ using while Loop Multiset in C++ 4 Pillars of OOPs Approach in C++ Backtracking Time Complexity in C++ C++ Global Variable C++ Pipe Tutorial Observer Design Pattern in C++ Private inheritance in C++ Pthread in C++ Parameters Pointers in C++ Abstract Factory Design Pattern in C++ Ascending order in C++ Call by Pointer in C++ Constexpr in C++ Deadlock in C++ Design Patterns in C++ Factory Method for Designing Pattern in C++ Name Mangling and extern in C++ Preventing Object Copy in C++ Quick Sort in C++ Single Handling in C++ Use of inheritance in C++ User-defined literals in C++ Vector methods in C++ Void * in C and C++ Zombie and Orphan Process in C++ List and Vector in C++ List iterators in C++ Merging Two Vectors in C++ Early Binding and Late Binding in C++ Factory Design Pattern in C++ Fisher-Yates shuffle algorithm in C++ for Auto in C++ Group anagrams in C++ Dynamic Casting in C++ 2D Vector initialization in C++ C++ GUI Visual Studio C++ IPC C++ Permutation Overloading Stream insertion in C++ Array sum in C++ STL C++ Define Macro C++ Design C++ Factory Pattern Convert String to Uppercase in C++ initializer list in C++ Iterator invalidation in C++ Lower bound in C++ Modulus of Two float numbers or double number Pass by value in C++ Stack size in C++ Unordered_map in C++ Binary String to int C++ Boost C++ Exception handling in constructor and destructor in C++ Explain class template in C++ Kadane Algorithm in C++ Map of Pairs in STL Pair in C++ Access Specifiers in C++ Add Two Numbers in C++ Using Class C++ Socket Programming Windows Cube root in C++ C++ Protected inheritance C++ Return Object Static Data Members in C++ Association in C++ Boost libraries in C++ Automatic Storage Class in C++ C++ Move Constructor Cast in C++ C++ 11 Lambda C++ Multithreading Bottom-up Approach in C++ C++ Static Class C++ Static Member C++ Static Variable C++ Template Class Implementation Kruskals Algorithm in C++ Kth Permutation Sequence in C++ Kth Smallest Element Using Priority Queue in C++ Min Heap in C++ Multilevel inheritance in C++ Playfair Cipher Algorithm in C++ Exception Handling in Java and C++ Sorting in C++ Time and Space Complexity for Loops in C++ Convert Vector To String in C++ Cascading in C++ Control Structure in C++ Passing Object as argument in C++ Vector Pair in C++ String Data Types in C++ Topological Sort in C++ C++ Move Semantics C++ Static Library Linking Call by Value and Call by Reference in C++ Data Structures algorithms and application in C++ Dereferencing a Pointer in C++ Linked List in C++ All Swing Components in C++ anonymous Object in C++ Cerr in C++ Control Flow Statement in C++ cstdlib in C++ Exception Objects in C++ Base Class and Derived Class in C++ Creating A Menu in C++ Escape Sequence in C++ Explicit in C++ int range in C++ Maximum Value in Vector in C++ NPTEL Programming in C++ Shared Pointer in C++ Static Member Function in C++ With Example The Diamond Pattern in C++ Const ptr C++ Const_Cast C++ Area Of Triangle in C++ Array input in C++ Cin String in C++ Coroutine in C++ Gui Design in C++ integer in C++ Advantages and Disadvantages of inheritance in C++ C++ IDE Linux C++ Mini Project With Source Code And Output C++ Variables Types Containers in C++ Dynamic Binding in C++ Explain Access Specifiers in C++ Iomanip in C++ Noexcept in C++ C++ Reference Initializer in C++ Constant Arguments in C++ Vector in C++ Stl Singleton Pattern in C++ Error Handling in C++ C++ Thread Id to Int C Str in C++ C++ Shared Ptr Scope Resolution Operator in C++ C++ Random Number Between 1 and 10 File Opening Mode in C++ New and Delete in C++ Big Integers in C++ Stack Unwinding in C++ C++ Syntax Link Map cbegin() and cend() function in C++ STL Hamming Code Implementation in C++ Files and Streams in C++ Private Destructor in C++ Semaphore in C++ Map Emplace_hint() function in C++ STL Complex Number Program in C++ Meta Classes in C++ C++ Delegates Custom Sort in C++ RAII in C++ Babylonian Square Root Algorithm in C++ File Input and output operation in C++ Sum of Digits of a Number in C++ C++ Type Traits Binary Search Tree Program in C++ Tree in C++ Built in Types in C++ Catch all Exceptions in C++ C++ Template Class Declaration and Definition C++ Generic Programming Introduction Fundamental Data Types in C++ API in C++ Menu Driven Program in C++ Exception Specification in C++ Bit Manipulation in C++ Dynamic Initialization Of Objects in C++ Returning Object from a Function in C++ Class and Structure in C++ Edmonds Karp Algorithm in C++ Flush in C++ Find Substring in C++ Input and Output Operators in C++ Final in C++ Lvalue and Rvalue in C++ C++ Singleton File Stream in C++ Has a Relationship in C++ Character Set in C++ Menu Driven Program in C++ Final Keyword in C++ Associative Containers in C++ Decltype in C++ Insert Function in C++ Metaclass in C++ Move Constructor in C++ Move Semantics in C++

For Auto in C++


The original and updated meanings of this keyword are specified in the C++ standard. Prior to Visual Studio 2010, the "auto" keyword declared a local lifetime variable that is in the automatic storage class. The auto keyword defines a variable whose type is determined by the initialization statement in its declaration as of Visual Studio 2010 onward. The auto keyword's meaning is controlled by the /Zc:auto[-] compiler option.


auto declarator initializer ;
[](auto parameter1 , auto parameter2 ) {};


The “auto” keyword instructs the compiler to determine the type of a lambda expression parameter or declared variable from its initialization expression.

Unless you truly desire a conversion, we advise using the auto keyword because it offers the following advantages:

  • Robustness: It simply functions even when the type of the expression changes, including when the type of a function returns changes.
  • Performance: There won't be any conversion, you can count on it.
  • Usability: You do not have to be concerned about typos or name-spelling errors.
  • Efficiency: There is room for improvement in your coding.

Cases of conversion where using auto might not be a good idea include:

  • Nothing less than the desired type will do.
  • Using the auxiliary types for expressions, for instance, (valarray+valarray).

When declaring a variable, the auto keyword should be used in place of the type and an initialization phrase. Additionally, specifiers and declarators like pointer (*), const, reference (&), rvalue reference (&&) and volatile can be used to change the auto keyword (&&). The initialization expression is evaluated by the compiler, which then makes use of the results to determine the type of the variable.

There are various variations of the auto initialization expression:

  • The syntax for universal initialization, such as auto a { 42 };
  • the syntax for assignments, like auto x = 0;
  • The two preceding versions are combined in universal assignment syntax, such as auto c = 3.14159;.
  • Initialization is done directly or using constructor-style syntax, like auto d(1.41421f);.

A distinct initialization syntax is used when the auto is utilized to define the loop parameter in a range based on a statement, such as for (auto& I iterable) do action(i);.

The auto keyword serves as a stand-in for a type but is not a type in and of itself. As a result, the auto keyword cannot be used with operators like sizeof or (for C++/CLI) typeid or with casts.


A straightforward method to define a variable with a complex type is to use the auto keyword. When the initialization statement contains pointers to functions, templates, or pointers to members, for instance, you can define a variable using auto.

A variable can be declared and initialized to a lambda expression using auto as well. Since only the compiler is aware of the type of a lambda expression, you cannot define the type of the variable yourself. 

Types of Trailing Returns

To assist in creating template libraries, utilize auto and the decltype type specifier. Declare a function template whose return type depends on the types of its template arguments using auto and decltype. Alternately, you can declare a function template using auto and decltype that wraps a call to some other function and returns whatever that other function's return type is.

CV Qualifications and References

Utilizing volatile qualifiers, const qualifiers, and auto drops references. Think about the following instance:


#include <iostream>
using namespace std;

int main( )
    int c = 10;
    int&count_Ref = c;
    auto my_Auto = count_Ref;

count_Ref = 11;
cout<< c << " ";

my_Auto = 12;
cout<< c <<endl;


[Running] cd "d:\Programming\C++\" && g++ test.cpp -o test && "d:\Programming\C++\"test
11 11

[Done] exited with code=0 in 0.773 seconds

Because my_Auto is an "int", not an int reference, the output in the previous example is 11 11, rather than 11 12, as it would have been if auto hadn't lost the reference qualifier.

Braced Initializers and Type Deduction (C++14)

Braces are used to initialize an auto variable in the following piece of code. Keep in mind the difference between b and c as well as a and e.


#include <initializer_list>

int main()
    auto a = { 2, 3 }; // std::initializer_list<int>

    auto b = { 4 }; // std::initializer_list<int>

    auto c{ 5 };  // int

    // C3535: 'auto' type cannot be determined from the initializer list'
    auto d = { 6, 7.7 };

    // The type for "auto" in C3518 can only be determined from a single initializer phrase in a context including direct-list initialization.
    auto e{ 9, 10 };

    return 0;


[Running] cd "d:\Programming\C++\" && g++ tempCodeRunnerFile.cpp -o tempCodeRunnerFile&& "d:\Programming\C++\"tempCodeRunnerFile
tempCodeRunnerFile.cpp: In function 'int main()':
tempCodeRunnerFile.cpp:12:23: error: unable to deduce 'std::initializer_list<auto>' from '{6, 7.7000000000000002e+0}'
     auto d = { 6, 7.7 };
tempCodeRunnerFile.cpp:12:23: note:   deduced conflicting types for parameter 'auto' ('int' and 'double')
tempCodeRunnerFile.cpp:15:19: error: direct-list-initialization of 'auto' requires exactly one element [-fpermissive]
     auto e{ 9, 10 };
tempCodeRunnerFile.cpp:15:19: note: for deduction to 'std::initializer_list', use copy-list-initialization (i.e. add '=' before the '{')

[Done] exited with code=1 in 0.157 seconds

Error Messages and Restrictions

The following table details the limitations on the usage of the auto keyword as well as the diagnostic error message the compiler generates when those limitations are met.

Error numberDescription
C3530Any other type of specifier cannot be used with the “auto” keyword.
C3531An initializer is required for symbols that are specified using the “auto” keyword.
C3532You erroneously declared a type using the “auto” keyword. You might have declared an array or a method return type, for instance.
C3533, C3539The “auto” keyword cannot be used to declare either a parameter or a template argument.
C3534The “auto” keyword cannot be used to declare a method or template parameter.
C3535A symbol must first be initialized before it can be utilized. The practical implication is that a variable cannot be used to initialize itself.
C3536A type that is specified with the “auto” keyword cannot be cast.
C3538A declarator list with the “auto” keyword defined must resolve each symbol to the same type. 
C3540, C3541A symbol that has the “auto” keyword in its declaration cannot be subjected to the "sizeof" and "typeid" operators.


These bits of code serve as examples of several possible uses for the auto keyword.

The declarations that follow are interchangeable. The type of variable i is specified to be int in the first sentence. Because initialization expression (0) is an integer, it can be assumed that variable j in the second sentence is of type int.


// The explicit type of variable i is int.
int i = 0;  
// Because zero is an integer, the variable jhas the implicit type of int.
auto j = 0;

The declarations that follow are identical, but the second one is easier to understand. The convenience of using the “auto” keyword is among its most appealing arguments.


map<int,list<string>>::iterator k = m.begin();
auto k = m.begin();

When the "for" and range for loops begin, the following code piece declares the types of the variables itr and elm.


#include <deque>
using namespace std;

int main()
    deque<double>dq_Double_Data(10, 0.1);

    for (auto itr = dq_Double_Data.begin(); itr != dq_Double_Data.end(); ++itr)
    { /* ... */ }

    // Keeping the following information in mind, choose range-for loops
    //(Any range-for with auto is affected by this, not just deque)

    // COPIES elements, which is only somewhat better than the other examples.
    for (auto elm :dq_Double_Data) 
    { /* ... */ }

    // observes elements IN-PLACE and/or adjusts them
    for (auto&elm :dq_Double_Data) 
    { /* ... */ }

    // examines elements IN-PLACE
    for (const auto&elm :dq_Double_Data) 
    { /* ... */ }

The “new” operator and a pointer declaration are used to declare pointers in the following code segment.


double a = 12.34;
auto *b = new auto(a), **c = new auto(&b);

The following snippet of code includes several symbol declarations in every declaration statement. Keep in mind that each statement's symbols are all resolved to the same type.


// Resolves to int.
auto a = 1, *b = &a, **c = &b; 
// Resolves to double.
auto x(2.01), *y (&a);   
// Resolves to char.      
auto z = 'x', *p(&z);    
// Resolves to int.      
auto n = 1, &m = n;     

The conditional operator (?:) is used in the following code fragment to declare variable x as an integer with the value 300:


int v_1 = 100, v_2 = 300;
auto x = v_1 > v_2 ? v_1 : v_2;

The code snippet that follows initializes the variables a to be of type int, b to be a reference to a variable of type const int, and fun_p to be a pointer to the function that returns a variable of type int.


int fun(int a) 
{ return a; }
int main()
    auto a = fun(0);
    const auto& b = fun(1);
    int (*ptr)(int a);
ptr = fun;
    auto fun_p = ptr;