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C++ Programming Code Examples

C++ > Code Snippets Code Examples

A Class as a Member Variable of Another Class

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/* A Class as a Member Variable of Another Class This is an example of one object (the shape class implements a rectangle) being a member variable of another object (a brick). */ Header File: shape.h #ifndef _SHAPE_H #define _SHAPE_H class FRectangle { public: FRectangle(double l = 0, double w = 0) : Length(l), Width(w) {} void setLength(double lgt); void setWidth(double wdt); double getLength() const; double getWidth() const; double Perimeter() const; double Area() const; void Properties(); private: double Length; double Width; }; #endif // _SHAPE_H Source File: shape.cpp #include <iostream.h> #include "shape.h" void FRectangle::setLength(double lgt) { Length = lgt; } void FRectangle::setWidth(double wdt) { Width = wdt; } double FRectangle::getLength() const { return Length; } double FRectangle::getWidth() const { return Width; } double FRectangle::Perimeter() const { return 2 * (Length + Width); } double FRectangle::Area() const { return Length * Width; } void FRectangle::Properties() { cout << "\nRectangle characteristics"; cout << "\n\tLength = " << Length; cout << "\n\tWidth = " << Width; cout << "\n\tPerimeter = " << Perimeter(); cout << "\n\tArea = " << Area() << endl; } Header File: brick.h #ifndef BRICK_H_ #define BRICK_H_ #include "shape.h" class Brick { public: Brick() {} void setThickness(double Tck); void setDimensions(double l, double w, double t); void setColor(char* clr); void setTexture(char* txr); char* getColor() const; char* getTexture() const; double Volume() const; void Display(); private: FRectangle shape; char* Color; char* Texture; double Thickness; }; #endif // BRICK_H_ Source File: brick.cpp #include <iostream.h> #include "brick.h" void Brick::setThickness(double Tck) { Thickness = Tck; } void Brick::setColor(char* clr) { Color = clr; } void Brick::setTexture(char* txr) { Texture = txr; } void Brick::setDimensions(double l, double w, double t) { shape.setLength(l); shape.setWidth(w); setThickness(t); } char* Brick::getColor() const { return Color; } char* Brick::getTexture() const { return Texture; } double Brick::Volume() const { return shape.getLength() * shape.getWidth() * Thickness; } void Brick::Display() { cout << "\nBrick characteristics"; cout << "\n\tLength = " << shape.getLength(); cout << "\n\tWidth = " << shape.getWidth(); cout << "\n\tArea = " << shape.Area(); cout << "\n\tVolume = " << Volume(); cout << "\n\tColor = " << getColor(); cout << "\n\tTextture = " << getTexture(); cout << endl; } Main File: Exo.cpp #include "shape.h" #include "brick.h" void main() { Brick brick; brick.setDimensions(12.50, 8.75, 5.55); brick.setColor("Bone White"); brick.setTexture("Early Breeze"); brick.Display(); } Here is an example of running the program: Brick characteristics Length = 12.5 Width = 8.75 Area = 109.375 Volume = 607.031 Color = Bone White Textture = Early Breeze
Classes and Objects in C++ Language
The main purpose of C++ programming is to add object orientation to the C programming language and classes are the central feature of C++ that supports object-oriented programming and are often called user-defined types. A class is used to specify the form of an object and it combines data representation and methods for manipulating that data into one neat package. The data and functions within a class are called members of the class.
C++ Class Definitions
When you define a class, you define a blueprint for a data type. This doesn't actually define any data, but it does define what the class name means, that is, what an object of the class will consist of and what operations can be performed on such an object. A class definition starts with the keyword class followed by the class name; and the class body, enclosed by a pair of curly braces. A class definition must be followed either by a semicolon or a list of declarations. For example, we defined the Box data type using the keyword class as follows:
class Box { public: double length; // Length of a box double breadth; // Breadth of a box double height; // Height of a box };
The keyword public determines the access attributes of the members of the class that follows it. A public member can be accessed from outside the class anywhere within the scope of the class object. You can also specify the members of a class as private or protected which we will discuss in a sub-section.
Define C++ Objects
A class provides the blueprints for objects, so basically an object is created from a class. We declare objects of a class with exactly the same sort of declaration that we declare variables of basic types. Following statements declare two objects of class Box:
Box Box1; // Declare Box1 of type Box Box Box2; // Declare Box2 of type Box
Both of the objects Box1 and Box2 will have their own copy of data members.
Accessing the Data Members
The public data members of objects of a class can be accessed using the direct member access operator (.). It is important to note that private and protected members can not be accessed directly using direct member access operator (.).
Classes and Objects in Detail
There are further interesting concepts related to C++ Classes and Objects which we will discuss in various sub-sections listed below: • Class Member Functions: A member function of a class is a function that has its definition or its prototype within the class definition like any other variable. • Class Access Modifiers: A class member can be defined as public, private or protected. By default members would be assumed as private. • Constructor & Destructor: A class constructor is a special function in a class that is called when a new object of the class is created. A destructor is also a special function which is called when created object is deleted. • Copy Constructor: The copy constructor is a constructor which creates an object by initializing it with an object of the same class, which has been created previously. • Friend Functions: A friend function is permitted full access to private and protected members of a class. • Inline Functions: With an inline function, the compiler tries to expand the code in the body of the function in place of a call to the function. • this Pointer: Every object has a special pointer this which points to the object itself. • Pointer to C++ Classes: A pointer to a class is done exactly the same way a pointer to a structure is. In fact a class is really just a structure with functions in it. • Static Members of a Class: Both data members and function members of a class can be declared as static.
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/* using public and private in C++ Class */ // Program to illustrate the working of // public and private in C++ Class #include <iostream> using namespace std; class Room { private: double length; double breadth; double height; public: // function to initialize private variables void initData(double len, double brth, double hgt) { length = len; breadth = brth; height = hgt; } double calculateArea() { return length * breadth; } double calculateVolume() { return length * breadth * height; } }; int main() { // create object of Room class Room room1; // pass the values of private variables as arguments room1.initData(42.5, 30.8, 19.2); cout << "Area of Room = " << room1.calculateArea() << endl; cout << "Volume of Room = " << room1.calculateVolume() << endl; return 0; }
#include Directive in C++
#include is a way of including a standard or user-defined file in the program and is mostly written at the beginning of any C/C++ program. This directive is read by the preprocessor and orders it to insert the content of a user-defined or system header file into the following program. These files are mainly imported from an outside source into the current program. The process of importing such files that might be system-defined or user-defined is known as File Inclusion. This type of preprocessor directive tells the compiler to include a file in the source code program.
Syntax for #include Directive in C++
#include "user-defined_file"
Including using " ": When using the double quotes(" "), the preprocessor access the current directory in which the source "header_file" is located. This type is mainly used to access any header files of the user's program or user-defined files.
#include <header_file>
Including using <>: While importing file using angular brackets(<>), the the preprocessor uses a predetermined directory path to access the file. It is mainly used to access system header files located in the standard system directories. Header File or Standard files: This is a file which contains C/C++ function declarations and macro definitions to be shared between several source files. Functions like the printf(), scanf(), cout, cin and various other input-output or other standard functions are contained within different header files. So to utilise those functions, the users need to import a few header files which define the required functions. User-defined files: These files resembles the header files, except for the fact that they are written and defined by the user itself. This saves the user from writing a particular function multiple times. Once a user-defined file is written, it can be imported anywhere in the program using the #include preprocessor. • In #include directive, comments are not recognized. So in case of #include <a//b>, a//b is treated as filename. • In #include directive, backslash is considered as normal text not escape sequence. So in case of #include <a\nb>, a\nb is treated as filename. • You can use only comment after filename otherwise it will give error.
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/* using #include directive in C language */ #include <stdio.h> int main() { /* * C standard library printf function * defined in the stdio.h header file */ printf("I love you Clementine"); printf("I love you so much"); printf("HappyCodings"); return 0; }
main() Function in C++
A program shall contain a global function named main, which is the designated start of the program in hosted environment. main() function is the entry point of any C++ program. It is the point at which execution of program is started. When a C++ program is executed, the execution control goes directly to the main() function. Every C++ program have a main() function.
Syntax for main() Function in C++
void main() { ............ ............ }
void is a keyword in C++ language, void means nothing, whenever we use void as a function return type then that function nothing return. here main() function no return any value.
main is a name of function which is predefined function in C++ library. In place of void we can also use int return type of main() function, at that time main() return integer type value. 1) It cannot be used anywhere in the program a) in particular, it cannot be called recursively b) its address cannot be taken 2) It cannot be predefined and cannot be overloaded: effectively, the name main in the global namespace is reserved for functions (although it can be used to name classes, namespaces, enumerations, and any entity in a non-global namespace, except that a function called "main" cannot be declared with C language linkage in any namespace). 3) It cannot be defined as deleted or (since C++11) declared with C language linkage, constexpr (since C++11), consteval (since C++20), inline, or static. 4) The body of the main function does not need to contain the return statement: if control reaches the end of main without encountering a return statement, the effect is that of executing return 0;. 5) Execution of the return (or the implicit return upon reaching the end of main) is equivalent to first leaving the function normally (which destroys the objects with automatic storage duration) and then calling std::exit with the same argument as the argument of the return. (std::exit then destroys static objects and terminates the program). 6) (since C++14) The return type of the main function cannot be deduced (auto main() {... is not allowed). 7) (since C++20) The main function cannot be a coroutine.
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/* simple code example by main() function in C++ */ #include <iostream> using namespace std; int main() { int day = 4; switch (day) { case 1: cout << "Monday"; break; case 2: cout << "Tuesday"; break; case 3: cout << "Wednesday"; break; case 4: cout << "Thursday"; break; case 5: cout << "Friday"; break; case 6: cout << "Saturday"; break; case 7: cout << "Sunday"; break; } return 0; }
#define Directive in C++
In the C++ Programming Language, the #define directive allows the definition of macros within your source code. These macro definitions allow constant values to be declared for use throughout your code. Macro definitions are not variables and cannot be changed by your program code like variables. You generally use this syntax when creating constants that represent numbers, strings or expressions. The syntax for creating a constant using #define in the C++ is: #define token value
Syntax for #define Directive in C++
#define macro-name replacement-text
• Using #define to create Macros Macros also follow the same structure as Symbolic Constants; however, Macros allow arguments to be included in the identifier:
#define SQUARE_AREA(l) ((l) * (l))
Unlike in functions, the argument here is enclosed in parenthesis in the identifier and does not have a type associated with it. Before compilation, the compiler will replace every instance of SQUARE_AREA(l) by ((l) * (l)), where l can be any expression. • Conditional Compilation There are several directives, which can be used to compile selective portions of your program's source code. This process is called conditional compilation. The conditional preprocessor construct is much like the 'if' selection structure. Consider the following preprocessor code:
#ifndef NULL #define NULL 0 #endif
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/* #define directive in C++ language */ #include <bits/stdc++.h> using namespace std; void func1(); void func2(); #pragma startup func1 #pragma exit func2 void func1() { cout << "Inside func1()\n"; } void func2() { cout << "Inside func2()\n"; } int main() { void func1(); void func2(); cout << "Inside main()\n"; return 0; }
setcolor() Function in C++
setcolor() function is used to set the foreground color in graphics mode. After resetting the foreground color you will get the text or any other shape which you want to draw in that color. setcolor sets the current drawing color to color, which can range from 0 to getmaxcolor. The current drawing color is the value to which pixels are set when lines, and so on are drawn. The drawing colors shown below are available for the CGA and EGA, respectively.
Syntax for setcolor() Function in C++
void setcolor(int color);
specify the color setcolor() functions contains only one argument that is color. It may be the color name enumerated in graphics.h header file or number assigned with that color. This function does not return any value. INT VALUES corresponding to Colors: • BLACK 0 • BLUE 1 • GREEN 2 • CYAN 3 • RED 4 • MAGENTA 5 • BROWN 6 • LIGHTGRAY 7 • DARKGRAY 8 • LIGHTBLUE 9 • LIGHTGREEN 10 • LIGHTCYAN 11 • LIGHTRED 12 • LIGHTMAGENTA 13 • YELLOW 14 • WHITE 15
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/* setcolor() function change the current drawing color in graphic mode. */ #include<stdio.h> #include<conio.h> #include<graphics.h> void main() { int gd=DETECT,gm; initgraph(&gd,&gm," "); setbkcolor(5);//set background color setcolor(11);//color of time settextstyle(4, HORIZ_DIR, 8);//font of time setcolor(GREEN); circle(320,240,100); setcolor(RED); outtextxy(320,80."It is circle"); getch(); closegraph(); }
#ifndef Directive in C++
The #ifndef directive of the C++ Programming Language helps in allowing the conditional compilation. The C++ Programming Language's preprocessor helps in determining only if the macro provided is not at all existed before including the specific subsequent code in the C++ compilation process. The #ifndef preprocessor only checks If the specific macro is not at all defined with the help of the #define directive. If the condition is TRUE then it will be helpful in executing the code otherwise the else code of the #ifndef will be compiled or executed only if present.
Syntax for #ifndef Directive in C++
#ifndef MACRO //Code Statements #else //Code Statements which are used to include if the specific token is defined #endif
#ifndef MACRO
The #ifndef works for the opposite condition of the #ifdef directive of the C Programming Language. The "MACRO" definition should not be defined for the specific preprocessor which is used to include the C Programming Source Code into the specific compiled application. The #ifndef must be ended with the #endif directive of the C Programming Language.
#else directive
If the #ifndef does not accept then else code statements will be printed which are actually used in including the specific which is defined.
#endif directive
The #endif directive of the C Programming Language helps in closing the #ifndef directive of the C Programming Language. It is must and should end only with the #endif C Source code directive. The $ifndef directive usually checks/helps in seeing the specific identifier is currently not defined or not. The #ifndef preprocessor of the C Programming Language helps in allowing the conditional compilations. The preprocessor directive helps in determining whether the macro is existed or not before the subsequent code in the compilation process/ procedure. The #ifndef directive and #if !defined identifier are equivalent directives of the C Programming Language. The #ifndef directive helps in checking the opposite condition of the #ifdef directive of the C Programming Language. If the specified identifier is not even defined or definition is removed with the help of the #undef then the condition is TRUE for nonzero value or else the condition will be FALSE.
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/* #ifndef Directive in C++ language */ #define Module101 #define MyVersion 1.1 #include<iostream> usingnamespace std; int main(void) { cout<<"Sample using #define, #ifdef, #ifndef"<<endl; cout<<" #undef, #else and #endif..."<<endl; cout<<"-------------------------------------"<<endl; #ifdef Module102 cout<<"\nModule102 is defined."<<endl; #else cout<<"\nModule102 is not defined."<<endl; #endif #ifndef MyVersion cout<<"\nMyVersion is not defined"<<endl; #else cout<<"\nMyVersion is "<<MyVersion<<endl; #endif #ifdef MyRevision cout<<"\nMy Revision is defined\n"<<endl; #else cout<<"\nMyRevision is not defined!"<<endl<<endl; #endif #undef MyVersion #ifndef MyVersion cout<<"MyVersion is not defined"<<endl<<endl; #else cout<<"MyVersion is "<<MyVersion<<endl; #endif return 0; }
length() Function in C++
Return length of string. Returns the length of the string, in terms of bytes. This function is used to find the length of the string in terms of bytes. This is the actual number of bytes that conform the contents of the string , which is not necessarily equal to the storage capacity. This is the number of actual bytes that conform the contents of the string, which is not necessarily equal to its storage capacity. Note that string objects handle bytes without knowledge of the encoding that may eventually be used to encode the characters it contains. Therefore, the value returned may not correspond to the actual number of encoded characters in sequences of multi-byte or variable-length characters (such as UTF-8).
Syntax for length() Function in C++
size_t length() const noexcept;
This function does not accept any parameter. Function returns the number of bytes in the string. size_t is an unsigned integral type (the same as member type string::size_type). Both string::size and string::length are synonyms and return the exact same value. The length() function is also defined inside the string.h header file and works in the same way size() does. Both functions return the same values and are also used in the same way. This function contains single parameter. This function returns the integer value in terms of bytes.
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/* return length of string by length() function code example */ #include<iostream> #include<cstring> using namespace std; main() { string myStr = "This is a sample string"; char myStrChar[] = "This is a sample string"; cout << "String length using string::length() function: " << myStr.length() <<endl; cout << "String length using string::size() function: " << myStr.size() <<endl; cout << "String length using strlen() function for c like string: " << strlen(myStrChar) <<endl; cout << "String length using while loop: "; char *ch = myStrChar; int count = 0; while(*ch != '\0'){ count++; ch++; } cout << count << endl; cout << "String length using for loop: "; count = 0; for(int i = 0; myStrChar[i] != '\0'; i++){ count++; } cout << count; }
Constructors in C++ Language
In C++, constructor is a special method which is invoked automatically at the time of object creation. It is used to initialize the data members of new object generally. The constructor in C++ has the same name as class or structure. Constructors are special class functions which performs initialization of every object. The Compiler calls the Constructor whenever an object is created. Constructors initialize values to object members after storage is allocated to the object. Whereas, Destructor on the other hand is used to destroy the class object. • Default Constructor: A constructor which has no argument is known as default constructor. It is invoked at the time of creating object.
Syntax for Default Constructor in C++
class_name(parameter1, parameter2, ...) { // constructor Definition }
• Parameterized Constructor: In C++, a constructor with parameters is known as a parameterized constructor. This is the preferred method to initialize member data. These are the constructors with parameter. Using this Constructor you can provide different values to data members of different objects, by passing the appropriate values as argument.
Syntax for Parameterized Constructor in C++
class class_name { public: class_name(variables) //Parameterized constructor declared. { } };
• Copy Constructors: These are special type of Constructors which takes an object as argument, and is used to copy values of data members of one object into other object.
Syntax for Copy Constructors in C++
classname (const classname &obj) { // body of constructor }
The copy constructor is a constructor which creates an object by initializing it with an object of the same class, which has been created previously. The copy constructor is used to - • Initialize one object from another of the same type. • Copy an object to pass it as an argument to a function. • Copy an object to return it from a function. If a copy constructor is not defined in a class, the compiler itself defines one.If the class has pointer variables and has some dynamic memory allocations, then it is a must to have a copy constructor. The most common form of copy constructor is shown here.
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/* A constructor is a special type of member function that is called automatically when an object is created. In C++, a constructor has the same name as that of the class and it does not have a return type. */ #include <iostream> using namespace std; // declare a class class Wall { private: double length; double height; public: // initialize variables with parameterized constructor Wall(double len, double hgt) { length = len; height = hgt; } // copy constructor with a Wall object as parameter // copies data of the obj parameter Wall(Wall &obj) { length = obj.length; height = obj.height; } double calculateArea() { return length * height; } }; int main() { // create an object of Wall class Wall wall1(10.5, 8.6); // copy contents of wall1 to wall2 Wall wall2 = wall1; // print areas of wall1 and wall2 cout << "Area of Wall 1: " << wall1.calculateArea() << endl; cout << "Area of Wall 2: " << wall2.calculateArea(); return 0; }
rectangle() Function in C++
rectangle() is used to draw a rectangle. Coordinates of left top and right bottom corner are required to draw the rectangle. left specifies the X-coordinate of top left corner, top specifies the Y-coordinate of top left corner, right specifies the X-coordinate of right bottom corner, bottom specifies the Y-coordinate of right bottom corner.
Syntax for rectangle() Function in C++
rectangle(int left, int top, int right, int bottom);
X coordinate of top left corner.
Y coordinate of top left corner.
X coordinate of bottom right corner.
Y coordinate of bottom right corner. To create a rectangle, you have to pass the four parameters in this function. The two parameters represent the left and top upper left corner. Similarly, the right bottom parameter represents the lower right corner of the rectangle. This function does not return any value.
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/* function rectangle() draws a rectangle in graphic mode. */ int main() { // location of left, top, right, bottom int left = 150, top = 150; int right = 450, bottom = 450; // initgraph initializes the graphics system // by loading a graphics driver from disk initgraph(&gd, &gm, ""); // rectangle function rectangle(left, top, right, bottom); left = 200, = 250; right = 150, = 300; rectangle(left, top, right, bottom); left = 100, = 200; right = 450, = 100; rectangle(left, top, right, bottom); getch(); return 0; }
width() Function in C++
Get/set field width. The first form (1) returns the current value of the field width. The second form (2) also sets a new field width for the stream. The field width determines the minimum number of characters to be written in some output representations. If the standard width of the representation is shorter than the field width, the representation is padded with fill characters at a point determined by the format flag adjustfield (one of left, right or internal). The fill character can be retrieved or changed by calling the member function fill. The format flag adjustfield can be modified by calling the member functions flags or setf, by inserting one of the following manipulators: left, right and internal, or by inserting the parameterized manipulator setiosflags. The field width can also be modified using the parameterized manipulator setw. Manages the minimum number of characters to generate on certain output operations and the maximum number of characters to generate on certain input operations. Returns the current field width. Sets the field width to the given one. Returns the previous field width.
Syntax for width() Function in C++
//get (1) streamsize width() const; //set (2) streamsize width (streamsize wide);
New value for the stream's field width. streamsize in signed integral type. Function returns the value of the field width before the call. Some I/O functions call width(0) before returning, see std::setw (this results in this field having effect on the next I/O function only, and not on any subsequent I/O) The exact effects this modifier has on the input and output vary between the individual I/O functions and are described at each operator<< and operator>> overload page individually.
Data races
Accesses (1) or modifies (2) the stream object. Concurrent access to the same stream object may cause data races.
Exception safety
Basic guarantee: if an exception is thrown, the stream is in a valid state.
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/* returns the current width, which is defined as the minimum number of characters to display with each output by function width() code example. */ //Adjusting the width of output #include <iostream.h> int main() { cout << "Start >"; cout.width(25); cout << 123 << "< End\n"; cout << "Start >"; cout.width(25); cout << 123<< "< Next >"; cout << 456 << "< End\n"; cout << "Start >"; cout.width(4); cout << 123456 << "< End\n"; return 0; }

Program sample, using a stack data strucure, computing whether the given "Parantheses" expression is 'valid' or not by check whether each parentheses is closed and nested in the
"Heapsort" can be thought of as an improved "selection sort": like that algorithm, it divides its input into a sorted and an unsorted region, and it iteratively shrinks the unsorted region