C++ Programming Code Examples
C++ > Data Structures Code Examples
C++ Program to Implement LRU Cache
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/* C++ Program to Implement LRU Cache
This C++ Program demonstrates the implementation of LRU Cache. */
#include <iostream>
#include <cstdlib>
#include <cmath>
using namespace std;
// A Queue Node (Queue is implemented using Doubly Linked List)
typedef struct QNode
{
QNode *prev, *next;
unsigned pageNumber;
} QNode;
// A Queue (A FIFO collection of Queue Nodes)
typedef struct Queue
{
unsigned count;
unsigned numberOfFrames;
QNode *front, *rear;
} Queue;
// A hash (Collection of pointers to Queue Nodes)
typedef struct Hash
{
int capacity;
QNode **array;
} Hash;
// A utility function to create a new Queue Node.
QNode* newQNode(unsigned pageNumber)
{
QNode* temp = new QNode;
temp->pageNumber = pageNumber;
temp->prev = temp->next = NULL;
return temp;
}
// A utility function to create an empty Queue.
Queue* createQueue(int numberOfFrames)
{
Queue* queue = new Queue;
queue->count = 0;
queue->front = queue->rear = NULL;
queue->numberOfFrames = numberOfFrames;
return queue;
}
// A utility function to create an empty Hash of given capacity
Hash* createHash(int capacity)
{
Hash* hash = new Hash;
hash->capacity = capacity;
hash->array = new QNode* [hash->capacity];
int i;
for(i = 0; i < hash->capacity; ++i)
hash->array[i] = NULL;
return hash;
}
// A function to check if there is slot available in memory
int AreAllFramesFull(Queue* queue)
{
return queue->count == queue->numberOfFrames;
}
// A utility function to check if queue is empty
int isQueueEmpty( Queue* queue )
{
return queue->rear == NULL;
}
// A utility function to delete a frame from queue
void deQueue( Queue* queue )
{
if (isQueueEmpty(queue))
return;
if (queue->front == queue->rear)
queue->front = NULL;
QNode* temp = queue->rear;
queue->rear = queue->rear->prev;
if (queue->rear)
queue->rear->next = NULL;
free(temp);
queue->count--;
}
// A function to add a page with given 'pageNumber' to both queue and hash
void Enqueue(Queue* queue, Hash* hash, unsigned pageNumber)
{
if (AreAllFramesFull(queue))
{
hash->array[queue->rear->pageNumber] = NULL;
deQueue(queue);
}
QNode* temp = newQNode(pageNumber);
temp->next = queue->front;
if (isQueueEmpty(queue))
queue->rear = queue->front = temp;
else
{
queue->front->prev = temp;
queue->front = temp;
}
hash->array[pageNumber] = temp;
queue->count++;
}
// This function is called when a page with given 'pageNumber' is referenced from cache (or memory).
void ReferencePage(Queue* queue, Hash* hash, unsigned pageNumber)
{
QNode* reqPage = hash->array[pageNumber];
if (reqPage == NULL)
Enqueue(queue, hash, pageNumber);
else if (reqPage != queue->front)
{
reqPage->prev->next = reqPage->next;
if (reqPage->next)
reqPage->next->prev = reqPage->prev;
if (reqPage == queue->rear)
{
queue->rear = reqPage->prev;
queue->rear->next = NULL;
}
reqPage->next = queue->front;
reqPage->prev = NULL;
reqPage->next->prev = reqPage;
queue->front = reqPage;
}
}
// Main
int main()
{
Queue* q = createQueue(4);
Hash* hash = createHash( 10 );
ReferencePage(q, hash, 1);
ReferencePage(q, hash, 2);
ReferencePage(q, hash, 3);
ReferencePage(q, hash, 1);
ReferencePage(q, hash, 4);
ReferencePage(q, hash, 5);
cout<<q->front->pageNumber<<" ";
cout<<q->front->next->pageNumber<<" ";
cout<<q->front->next->next->pageNumber<<" ";
cout<<q->front->next->next->next->pageNumber<<" ";
return 0;
}
Memory Management new Operator in C++
Allocate storage space. Default allocation functions (single-object form).
A new operator is used to create the object while a delete operator is used to delete the object. When the object is created by using the new operator, then the object will exist until we explicitly use the delete operator to delete the object. Therefore, we can say that the lifetime of the object is not related to the block structure of the program.
Syntax for new Operator in C++
#include <new>
//throwing (1)
void* operator new (std::size_t size);
//nothrow (2)
void* operator new (std::size_t size, const std::nothrow_t& nothrow_value) noexcept;
//placement (3)
void* operator new (std::size_t size, void* ptr) noexcept;
size
Size in bytes of the requested memory block. This is the size of the type specifier in the new-expression when called automatically by such an expression.
If this argument is zero, the function still returns a distinct non-null pointer on success (although dereferencing this pointer leads to undefined behavior). size_t is an integral type.
nothrow_value
The constant nothrow. This parameter is only used to distinguish it from the first version with an overloaded version. When the nothrow constant is passed as second parameter to operator new, operator new returns a null-pointer on failure instead of throwing a bad_alloc exception.
nothrow_t is the type of constant nothrow.
ptr
A pointer to an already-allocated memory block of the proper size. If called by a new-expression, the object is initialized (or constructed) at this location.
For the first and second versions, function returns a pointer to the newly allocated storage space.
For the third version, ptr is returned.
• (1) throwing allocation: Allocates size bytes of storage, suitably aligned to represent any object of that size, and returns a non-null pointer to the first byte of this block.
On failure, it throws a bad_alloc exception.
• (2) nothrow allocation: Same as above (1), except that on failure it returns a null pointer instead of throwing an exception. The default definition allocates memory by calling the the first version: ::operator new (size).
If replaced, both the first and second versions shall return pointers with identical properties.
• (3) placement: Simply returns ptr (no storage is allocated). Notice though that, if the function is called by a new-expression, the proper initialization will be performed (for class objects, this includes calling its default constructor).
The default allocation and deallocation functions are special components of the standard library; They have the following unique properties:
• Global: All three versions of operator new are declared in the global namespace, not within the std namespace.
• Implicit: The allocating versions ((1) and (2)) are implicitly declared in every translation unit of a C++ program, no matter whether header <new> is included or not.
• Replaceable: The allocating versions ((1) and (2)) are also replaceable: A program may provide its own definition that replaces the one provided by default to produce the result described above, or can overload it for specific types.
If set_new_handler has been used to define a new_handler function, this new-handler function is called by the default definitions of the allocating versions ((1) and (2)) if they fail to allocate the requested storage.
operator new can be called explicitly as a regular function, but in C++, new is an operator with a very specific behavior: An expression with the new operator, first calls function operator new (i.e., this function) with the size of its type specifier as first argument, and if this is successful, it then automatically initializes or constructs the object (if needed). Finally, the expression evaluates as a pointer to the appropriate type.
Data races
Modifies the storage referenced by the returned value. Calls to allocation and deallocation functions that reuse the same unit of storage shall occur in a single total order where each deallocation happens entirely before the next allocation.
This shall also apply to the observable behavior of custom replacements for this function.
Exception safety
The first version (1) throws bad_alloc if it fails to allocate storage.
Otherwise, it throws no exceptions (no-throw guarantee).
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/* C++ allows us to allocate the memory of a variable or an array in run time. This is known as dynamic memory allocation.
The new operator denotes a request for memory allocation on the Free Store. If sufficient memory is available, new operator initializes the memory and returns the address of the newly allocated and initialized memory to the pointer variable. */
/* Allocate storage space by operator new */
// C++ program code example to illustrate dynamic allocation and deallocation of memory using new and delete
#include <iostream>
using namespace std;
int main ()
{
// Pointer initialization to null
int* p = NULL;
// Request memory for the variable
// using new operator
p = new(nothrow) int;
if (!p)
cout << "allocation of memory failed\n";
else
{
// Store value at allocated address
*p = 29;
cout << "Value of p: " << *p << endl;
}
// Request block of memory
// using new operator
float *r = new float(75.25);
cout << "Value of r: " << *r << endl;
// Request block of memory of size n
int n = 5;
int *q = new(nothrow) int[n];
if (!q)
cout << "allocation of memory failed\n";
else
{
for (int i = 0; i < n; i++)
q[i] = i+1;
cout << "Value store in block of memory: ";
for (int i = 0; i < n; i++)
cout << q[i] << " ";
}
// freed the allocated memory
delete p;
delete r;
// freed the block of allocated memory
delete[] q;
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"
#include <header_file>
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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;
}
Standard Output Stream (cout) in C++
The cout is a predefined object of ostream class. It is connected with the standard output device, which is usually a display screen. The cout is used in conjunction with stream insertion operator (<<) to display the output on a console. On most program environments, the standard output by default is the screen, and the C++ stream object defined to access it is cout.
Syntax for cout in C++
cout << var_name;
//or
cout << "Some String";
<<
is the insertion operator
var_name
is usually a variable, but can also be an array element or elements of containers like vectors, lists, maps, etc.
The "c" in cout refers to "character" and "out" means "output". Hence cout means "character output".
The cout object is used along with the insertion operator << in order to display a stream of characters.
The << operator can be used more than once with a combination of variables, strings, and manipulators.
cout is used for displaying data on the screen. The operator << called as insertion operator or put to operator. The Insertion operator can be overloaded. Insertion operator is similar to the printf() operation in C. cout is the object of ostream class. Data flow direction is from variable to output device. Multiple outputs can be displayed using cout.
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/* standard output stream (cout) in C++ language */
#include <iostream>
using namespace std;
int main() {
string str = "Do not interrupt me";
char ch = 'm';
// use cout with write()
cout.write(str,6);
cout << endl;
// use cout with put()
cout.put(ch);
return 0;
}
Structures in C++ Language
In C++, classes and structs are blueprints that are used to create the instance of a class. Structs are used for lightweight objects such as Rectangle, color, Point, etc. Unlike class, structs in C++ are value type than reference type. It is useful if you have data that is not intended to be modified after creation of struct.
C++ Structure is a collection of different data types. It is similar to the class that holds different types of data.
Syntax for Structures in C++
struct structureName{
member1;
member2;
member3;
.
.
.
memberN;
};
struct Teacher
{
char name[20];
int id;
int age;
}
s.id = 4;
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/* Structure is a collection of variables of different data types under a single name. It is similar to a class in that, both holds a collecion of data of different data types. */
#include <iostream>
using namespace std;
struct Person
{
char name[50];
int age;
float salary;
};
int main()
{
Person p1;
cout << "Enter Full name: ";
cin.get(p1.name, 50);
cout << "Enter age: ";
cin >> p1.age;
cout << "Enter salary: ";
cin >> p1.salary;
cout << "\nDisplaying Information." << endl;
cout << "Name: " << p1.name << endl;
cout <<"Age: " << p1.age << endl;
cout << "Salary: " << p1.salary;
return 0;
}
Namespaces in C++ Language
Consider a situation, when we have two persons with the same name, jhon, in the same class. Whenever we need to differentiate them definitely we would have to use some additional information along with their name, like either the area, if they live in different area or their mother's or father's name, etc.
Same situation can arise in your C++ applications. For example, you might be writing some code that has a function called xyz() and there is another library available which is also having same function xyz(). Now the compiler has no way of knowing which version of xyz() function you are referring to within your code.
A namespace is designed to overcome this difficulty and is used as additional information to differentiate similar functions, classes, variables etc. with the same name available in different libraries. Using namespace, you can define the context in which names are defined. In essence, a namespace defines a scope.
Defining a Namespace
A namespace definition begins with the keyword namespace followed by the namespace name as follows:
namespace namespace_name {
// code declarations
}
name::code; // code could be variable or function.
Using Directive
You can also avoid prepending of namespaces with the using namespace directive. This directive tells the compiler that the subsequent code is making use of names in the specified namespace.
Discontiguous Namespaces
A namespace can be defined in several parts and so a namespace is made up of the sum of its separately defined parts. The separate parts of a namespace can be spread over multiple files.
So, if one part of the namespace requires a name defined in another file, that name must still be declared. Writing a following namespace definition either defines a new namespace or adds new elements to an existing one:
namespace namespace_name {
// code declarations
}
Nested Namespaces
Namespaces can be nested where you can define one namespace inside another name space as follows:
namespace namespace_name1 {
// code declarations
namespace namespace_name2 {
// code declarations
}
}
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/* namespaces in C++ language */
// A C++ code to demonstrate that we can define
// methods outside namespace.
#include <iostream>
using namespace std;
// Creating a namespace
namespace ns
{
void display();
class happy
{
public:
void display();
};
}
// Defining methods of namespace
void ns::happy::display()
{
cout << "ns::happy::display()\n";
}
void ns::display()
{
cout << "ns::display()\n";
}
// Driver code
int main()
{
ns::happy obj;
ns::display();
obj.display();
return 0;
}
If Else If Ladder in C/C++
The if...else statement executes two different codes depending upon whether the test expression is true or false. Sometimes, a choice has to be made from more than 2 possibilities. The if...else ladder allows you to check between multiple test expressions and execute different statements.
In C/C++ if-else-if ladder helps user decide from among multiple options. The C/C++ if statements are executed from the top down. As soon as one of the conditions controlling the if is true, the statement associated with that if is executed, and the rest of the C else-if ladder is bypassed. If none of the conditions is true, then the final else statement will be executed.
Syntax of if...else Ladder in C++
if (Condition1)
{ Statement1; }
else if(Condition2)
{ Statement2; }
.
.
.
else if(ConditionN)
{ StatementN; }
else
{ Default_Statement; }
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/* write a C program which demonstrate use of if-else-if ladder statement */
/* Program to Print Day Names using Else If Ladder in C++*/
#include <iostream>
using namespace std;
int main()
{
int day;
cout << "Enter Day Number: ";
cin >> day;
cout << "Day is ";
if (day == 1)
cout << "Sunday" << endl;
else if (day == 2)
cout << "Monday" << endl;
else if (day == 3)
cout << "Tuesday" << endl;
else if (day == 4)
cout << "Wednesday" << endl;
else if (day == 5)
cout << "Thursday" << endl;
else if (day == 6)
cout << "Friday" << endl;
else
cout << "Saturday" << endl;
return 0;
}
Standard Library free() Function in C++
Deallocate memory block. A block of memory previously allocated by a call to malloc, calloc or realloc is deallocated, making it available again for further allocations. If ptr does not point to a block of memory allocated with the above functions, it causes undefined behavior. If ptr is a null pointer, the function does nothing. Notice that this function does not change the value of ptr itself, hence it still points to the same (now invalid) location.
free() function in C++ <cstdlib> library is used to deallocate a memory block in C++. Whenever we call malloc, calloc or realloc function to allocate a memory block dynamically in C++, compiler allocates a block of size bytes of memory and returns a pointer to the start of the block. The new memory block allocated is not initialized but have intermediate values. free() method is used to free such block of memory. In case the pointer mentioned does not point to any memory block then it may lead to an undefined behavior, but does nothing in case of null pointer. Also after the memory block is made available still the pointer points to the same memory location.
Syntax for free() Function in C++
#include <cstdlib>
void free (void* ptr);
ptr
Pointer to a memory block previously allocated with malloc, calloc or realloc.
This function does not return any value.
• Here ptr refers to a pointer pointing to memory block in C++ that has been previously allocated by malloc, calloc or realloc. Here type of pointer is void because it is capable to hold any type of the pointer and can be cast to any type while dereferencing.
• In case pointer mentioned in free function is a null pointer then function does nothing as there is memory block for it to deallocate and returns nothing.
• And in case the pointer points to a memory block that has not been allocated using any one of malloc, calloc or realloc method then the behavior of free function can not be predicted.
The return type of free() function is void, that means this function returns nothing. All it does is simply deallocating the block of memory pointed by the referred pointer.
How free() Function work in C++?
• Free method is a great tool for dynamic memory management. It is present in <cstdlib> header file.
• When a memory block is allocated using std::malloc, std::calloc or std::alloc.a pointer is returned. This pointer is passed to free function, for deallocation. This helps in memory management for the compiler dynamically.
• In case the pointer is a null pointer then function does nothing as there is no memory being referenced by the pointer.
• As the datatype for the pointer is void then its is capable for dereferencing any type of pointer.
• In case the value of the pointer mentioned is not one allocated using these three methods then behavior of free function is undefined. Also it is undefined if the memory block being referenced by the pointer has already been deallocated using std::free or std::realloc method.
• This method has no impact on the pointer it just frees the memory block, pointer keep referring to the memory block.
• All the dynamic memory allocation and deallocation methods work in synchronize manner so that memory block being referred by the pointer for allocation must be free at that time.
Differences in delete and free in C++
delete()
• It is an operator.
• It de-allocates the memory dynamically.
• It should only be used either for the pointers pointing to the memory allocated using the new operator or for a NULL pointer.
• This operator calls the destructor after it destroys the allocated memory.
• It is faster.
free()
• It is a library function.
• It destroys the memory at the runtime.
• It should only be used either for the pointers pointing to the memory allocated using malloc() or for a NULL pointer.
• This function only frees the memory from the heap. It does not call the destructor.
• It is comparatively slower than delete as it is a function.
Data races
Only the storage referenced by ptr is modified. No other storage locations are accessed by the call.
If the function releases a unit of storage that is reused by a call to allocation functions (such as calloc or malloc), the functions are synchronized in such a way that the deallocation happens entirely before the next allocation.
Exceptions
No-throw guarantee: this function never throws exceptions.
If ptr does not point to a memory block previously allocated with malloc, calloc or realloc, and is not a null pointer, it causes undefined behavior.
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/* The free() function in C++ deallocates a block of memory previously allocated using calloc, malloc or realloc functions, making it available for further allocations code example. */
#include <iostream>
#include <cstdlib>
#include <cstring>
using namespace std;
int main()
{
char *ptr;
ptr = (char*) malloc(10*sizeof(char));
strcpy(ptr,"Hello C++");
cout << "Before reallocating: " << ptr << endl;
/* reallocating memory */
ptr = (char*) realloc(ptr,20);
strcpy(ptr,"Hello, Welcome to C++");
cout << "After reallocating: " <<ptr << endl;
free(ptr);
/* prints a garbage value after ptr is free */
cout << endl << "Garbage Value: " << ptr;
return 0;
}
For Loop Statement in C++
In computer programming, loops are used to repeat a block of code. For example, when you are displaying number from 1 to 100 you may want set the value of a variable to 1 and display it 100 times, increasing its value by 1 on each loop iteration. When you know exactly how many times you want to loop through a block of code, use the for loop instead of a while loop. A for loop is a repetition control structure that allows you to efficiently write a loop that needs to execute a specific number of times.
Syntax of For Loop Statement in C++
for (initialization; condition; update) {
// body of-loop
}
initialization
initializes variables and is executed only once.
condition
if true, the body of for loop is executed, if false, the for loop is terminated.
update
updates the value of initialized variables and again checks the condition.
A new range-based for loop was introduced to work with collections such as arrays and vectors.
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/* For Loop Statement in C++ Language */
// C++ program to find the sum of first n natural numbers
// positive integers such as 1,2,3,...n are known as natural numbers
#include <iostream>
using namespace std;
int main() {
int num, sum;
sum = 0;
cout << "Enter a positive integer: ";
cin >> num;
for (int i = 1; i <= num; ++i) {
sum += i;
}
cout << "Sum = " << sum << endl;
return 0;
}
If Else Statement in C++
In computer programming, we use the if statement to run a block code only when a certain condition is met. An if statement can be followed by an optional else statement, which executes when the boolean expression is false. There are three forms of if...else statements in C++:
• if statement,
• if...else statement,
• if...else if...else statement,
Syntax for If Statement in C++
if (condition) {
// body of if statement
}
Syntax for If...Else Statement
if (condition) {
// block of code if condition is true
}
else {
// block of code if condition is false
}
Syntax for If...Else...Else If Statement in C++
if (condition1) {
// code block 1
}
else if (condition2){
// code block 2
}
else {
// code block 3
}
Syntax for If Else If Ladder in C++
if (condition)
statement 1;
else if (condition)
statement 2;
.
.
else
statement;
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/* If Else Statement in C++ Language */
#include <iostream>
using namespace std;
int main () {
// local variable declaration:
int a = 100;
// check the boolean condition
if( a < 20 ) {
// if condition is true then print the following
cout << "a is less than 20;" << endl;
} else {
// if condition is false then print the following
cout << "a is not less than 20;" << endl;
}
cout << "value of a is : " << a << endl;
return 0;
}
What is an Array in C++ Language
An array is defined as the collection of similar type of data items stored at contiguous memory locations. Arrays are the derived data type in C++ programming language which can store the primitive type of data such as int, char, double, float, etc. It also has the capability to store the collection of derived data types, such as pointers, structure, etc. The array is the simplest data structure where each data element can be randomly accessed by using its index number.
C++ array is beneficial if you have to store similar elements. For example, if we want to store the marks of a student in 6 subjects, then we don't need to define different variables for the marks in the different subject. Instead of that, we can define an array which can store the marks in each subject at the contiguous memory locations.
By using the array, we can access the elements easily. Only a few lines of code are required to access the elements of the array.
Properties of Array
The array contains the following properties.
• Each element of an array is of same data type and carries the same size, i.e., int = 4 bytes.
• Elements of the array are stored at contiguous memory locations where the first element is stored at the smallest memory location.
• Elements of the array can be randomly accessed since we can calculate the address of each element of the array with the given base address and the size of the data element.
Advantage of C++ Array
• 1) Code Optimization: Less code to the access the data.
• 2) Ease of traversing: By using the for loop, we can retrieve the elements of an array easily.
• 3) Ease of sorting: To sort the elements of the array, we need a few lines of code only.
• 4) Random Access: We can access any element randomly using the array.
Disadvantage of C++ Array
• 1) Allows a fixed number of elements to be entered which is decided at the time of declaration. Unlike a linked list, an array in C++ is not dynamic.
• 2) Insertion and deletion of elements can be costly since the elements are needed to be managed in accordance with the new memory allocation.
Declaration of C++ Array
To declare an array in C++, a programmer specifies the type of the elements and the number of elements required by an array as follows
type arrayName [ arraySize ];
double balance[10];
Initializing Arrays
You can initialize an array in C++ either one by one or using a single statement as follows
double balance[5] = {850, 3.0, 7.4, 7.0, 88};
double balance[] = {850, 3.0, 7.4, 7.0, 88};
Accessing Array Elements
An element is accessed by indexing the array name. This is done by placing the index of the element within square brackets after the name of the array.
double salary = balance[9];
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/* arrays in C++ Language */
#include <iostream>
using namespace std;
int main() {
// initialize an array without specifying size
double numbers[] = {7, 5, 6, 12, 35, 27};
double sum = 0;
double count = 0;
double average;
cout << "The numbers are: ";
// print array elements
// use of range-based for loop
for (const double &n : numbers) {
cout << n << " ";
// calculate the sum
sum += n;
// count the no. of array elements
++count;
}
// print the sum
cout << "\nTheir Sum = " << sum << endl;
// find the average
average = sum / count;
cout << "Their Average = " << average << endl;
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
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
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;
}
Pointers in C++ Language
The pointer in C++ language is a variable, it is also known as locator or indicator that points to an address of a value. In C++, a pointer refers to a variable that holds the address of another variable. Like regular variables, pointers have a data type. For example, a pointer of type integer can hold the address of a variable of type integer. A pointer of character type can hold the address of a variable of character type.
You should see a pointer as a symbolic representation of a memory address. With pointers, programs can simulate call-by-reference. They can also create and manipulate dynamic data structures. In C++, a pointer variable refers to a variable pointing to a specific address in a memory pointed by another variable.
Syntax for Pointers in C++
int *ip; // pointer to an integer
double *dp; // pointer to a double
float *fp; // pointer to a float
char *ch // pointer to character
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/* pointer is a variable in C++ that holds the address of another variable */
#include <iostream>
using namespace std;
int main () {
int var = 20; // actual variable declaration.
int *ip; // pointer variable
ip = &var; // store address of var in pointer variable
cout << "Value of var variable: ";
cout << var << endl;
// print the address stored in ip pointer variable
cout << "Address stored in ip variable: ";
cout << ip << endl;
// access the value at the address available in pointer
cout << "Value of *ip variable: ";
cout << *ip << endl;
return 0;
}
This is a program from numerical to calculate the 'root' of the given system, it will check its conditions and perform the operation on that system, esle it will tell you that system is not
C++ program, "using iteration", implements the list of elements removed from the queue in first in first out mode using a Linked list. A linked list is an ordered set of data elements,