C++ Programming Code Examples
C++ > Arrays and Matrices Code Examples
Insert update delete element in array
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/* Insert update delete element in array
Write a c++ program which manages data in array having insert, update and delete value functions.
Program should be menu based properly asking for user to enter an option and on wrong or invalid input program should display proper message and ask user to enter value again.
This program is helpful to manage a menu base database using array and shows how to prevent from a wrong input. Its is of very basic level to introduce the simplest database management using array. It is recommended to copy the code make changes in it and examine output.
This code is managing a small database in array like insert, update and delete integer values in array
Program has global array declaration of size 10. Global declaration allows it accessible inside any function
A function name "Default values" is initializing all array indexes by default value of -1
A function name "Display Array" displays the array values using for loop
To manage the menu option do while is used and few if else statement within the loop to call a specific function on user selection
To restrict user to enter valid option recursion is used in two functions so if user enter invalid option For example array size is 10 and user select index number 11 then a message will be displayed function will call itself and user has to enter the option again */
#include <iostream>
#include <stdlib.h>
using namespace std;
//Global Array Declaration
int array[10];
void DisplayArray(){
for (int i=0;i<10;i++)
cout<< "Array [ "<<i<<" ] = "<<array[i]<<endl;
}
void SetDefaultValues(){
cout<<"Defalult Values :"<<endl;
for(int i=0;i<10;i++)
{
array[i]=-1;
cout<<"array ["<<i<<"]"<<"= "<<array[i]<<endl;
}
}
void InsertValues(){
cout<<"Enter 10 Values "<<endl;
for(int i=0;i<10;i++)
{
cin>>array[i];
}
cout<<"\n\t\t\tArray Values Inserted... Successfully "<<endl;
}
void DeleteValues(){
cout<<"Enter the Index Number To Delete Value :";
int index;
cin>>index;
if(index>9||index<0)
{
cout<<"Invalid Index Entered-> Valid Range(0-9)"<<endl;
DeleteValues();// Recall The Function it self
}
else
{
array[index]=-1;
}
cout<<"\n\t\t\tArray Value Deleted... Successfully "<<endl;
}
void UpdateValues(){
cout<<"Enter Index Number to Update Value :";
int index;
cin>>index;
if(index>9||index<0)
{
cout<<"Invalid Index Entered-> Valid Range(0-9)"<<endl;
UpdateValues();// Recall The Function it self
}
else
{
cout<<"Enter the New Value For Index array[ "<<index<<" ] = ";
cin>>array[index];
cout<<"\n\t\t\tArray Updated... Successfully "<<endl;
}
}
int main()
{
char option;
SetDefaultValues();
do
{
cout<<"\t\t\tEnter 1 to Enter Values\n\t\t\tEnter 2 to Update Values\n\t\t\tEnter 3 to Delete Values\n\n\t\t\t or Enter E to EXIT\n\n\t\t\t Enter Option: -> ";
cin>>option;
if(option=='1')
{
cout<<"Insert Function Called"<<endl;
InsertValues();
cout<<"Inserted Values :"<<endl;
DisplayArray();
}
else if(option=='2')
{
UpdateValues();
cout<<"Updated Array :"<<endl;
DisplayArray();
}
else if(option=='3')
{
DeleteValues();
cout<<"Array After Deleting Values :"<<endl;
DisplayArray();
}
else if(option!='e'&&option!='E')
{
cout<<"\n\n\t\t\tSelect A Valid Option From Below\n\n";
}
}while(option!='e'&&option!='E');
system("cls");// To Clear The Screen
cout<<"\n\n\n\n\n\n\n\n\n\n\t\tProgram Ended Press Any Key To Exit Screen.....\n\n\n\n\n\n\n\n\n\n\n\n"<<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;
}
system() Function in C++
Execute system command. Invokes the command processor to execute a command. If command is a null pointer, the function only checks whether a command processor is available through this function, without invoking any command.
The effects of invoking a command depend on the system and library implementation, and may cause a program to behave in a non-standard manner or to terminate.
Syntax for system() Function in C++
#include <cstdlib>
int system (const char* command);
command
C-string containing the system command to be executed. Or, alternatively, a null pointer, to check for a command processor.
If command is a null pointer, the function returns a non-zero value in case a command processor is available and a zero value if it is not.
If command is not a null pointer, the value returned depends on the system and library implementations, but it is generally expected to be the status code returned by the called command, if supported.
Data races
The function accesses the array pointed by command. Concurrently calling this function with a null pointer as argument is safe. Otherwise, it depends on the system and library implementation.
Exceptions
No-throw guarantee: this function does not throw exceptions. If command is not a null pointer, it causes undefined behavior.
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/* The system() function is a part of the C/C++ standard library. It is used to pass the commands that can be executed in the command processor or the terminal of the operating system, and finally returns the command after it has been completed. */
/* Execute system command by system() function code example */
// A C++ program that compiles and runs another C++ program
#include <bits/stdc++.h>
using namespace std;
int main ()
{
char filename[100];
cout << "Enter file name to compile ";
cin.getline(filename, 100);
// Build command to execute. For example if the input
// file name is a.cpp, then str holds "gcc -o a.out a.cpp"
// Here -o is used to specify executable file name
string str = "gcc ";
str = str + " -o a.out " + filename;
// Convert string to const char * as system requires
// parameter of type const char *
const char *command = str.c_str();
cout << "Compiling file using " << command << endl;
system(command);
cout << "\nRunning file ";
system("./a.out");
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 Input Stream (cin) in C++
The cin object is used to accept input from the standard input device i.e. keyboard. It is defined in the iostream header file. C++ cin statement is the instance of the class istream and is used to read input from the standard input device which is usually a keyboard. The extraction operator(>>) is used along with the object cin for reading inputs. The extraction operator extracts the data from the object cin which is entered using the keyboard.
Syntax for Standard Input Stream (cin) in C++
cin >> var_name;
>>
is the extraction operator.
var_name
is usually a variable, but can also be an element of containers like arrays, vectors, lists, etc.
The "c" in cin refers to "character" and "in" means "input". Hence cin means "character input".
The cin object is used along with the extraction operator >> in order to receive a stream of characters.
The >> operator can also be used more than once in the same statement to accept multiple inputs.
The cin object can also be used with other member functions such as getline(), read(), etc. Some of the commonly used member functions are:
• cin.get(char &ch): Reads an input character and stores it in ch.
• cin.getline(char *buffer, int length): Reads a stream of characters into the string buffer, It stops when:
it has read length-1 characters or
when it finds an end-of-line character '\n' or the end of the file eof.
• cin.read(char *buffer, int n): Reads n bytes (or until the end of the file) from the stream into the buffer.
• cin.ignore(int n): Ignores the next n characters from the input stream.
• cin.eof(): Returns a non-zero value if the end of file (eof) is reached.
The prototype of cin as defined in the iostream header file is: extern istream cin; The cin object in C++ is an object of class istream. It is associated with the standard C input stream stdin.
The cin object is ensured to be initialized during or before the first time an object of type ios_base::Init is constructed.
After the cin object is constructed, cin.tie() returns &cout. This means that any formatted input operation on cin forces a call to cout.flush() if any characters are pending for output.
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/* Standard Input Stream (cin) in C++ language */
// cin with Member Functions
#include <iostream>
using namespace std;
int main() {
char name[20], address[20];
cout << "Name: ";
// use cin with getline()
cin.getline(name, 20);
cout << "Address: ";
cin.getline(address, 20);
cout << endl << "You entered " << endl;
cout << "Name = " << name << endl;
cout << "Address = " << address;
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;
}
Logical Operators in C++
Logical Operators are used to compare and connect two or more expressions or variables, such that the value of the expression is completely dependent on the original expression or value or variable.
We use logical operators to check whether an expression is true or false. If the expression is true, it returns 1 whereas if the expression is false, it returns 0.
Assume variable A holds 1 and variable B holds 0:
&&
Called Logical AND operator. If both the operands are non-zero, then condition becomes true. (A && B) is false.
The logical AND operator && returns
true - if and only if all the operands are true.
false - if one or more operands are false.
||
Called Logical OR Operator. If any of the two operands is non-zero, then condition becomes true. (A || B) is true.
The logical OR operator || returns
true - if one or more of the operands are true.
false - if and only if all the operands are false.
!
Called Logical NOT Operator. Use to reverses the logical state of its operand. If a condition is true, then Logical NOT operator will make false. !(A && B) is true.
The logical NOT operator ! is a unary operator i.e. it takes only one operand.
It returns true when the operand is false, and false when the operand is true.
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/* The operator ! is the C++ operator for the Boolean operation NOT. It has only one operand, to its right, and inverts it, producing false if its operand is true, and true if its operand is false. Basically, it returns the opposite Boolean value of evaluating its operand.
The logical operators && and || are used when evaluating two expressions to obtain a single relational result. The operator && corresponds to the Boolean logical operation AND, which yields true if both its operands are true, and false otherwise. */
#include <iostream>
using namespace std;
main() {
int a = 5;
int b = 20;
int c ;
if(a && b) {
cout << "Line 1 - Condition is true"<< endl ;
}
if(a || b) {
cout << "Line 2 - Condition is true"<< endl ;
}
/* Let's change the values of a and b */
a = 0;
b = 10;
if(a && b) {
cout << "Line 3 - Condition is true"<< endl ;
} else {
cout << "Line 4 - Condition is not true"<< endl ;
}
if(!(a && b)) {
cout << "Line 5 - Condition is true"<< endl ;
}
return 0;
}
While Loop Statement in C++
In while loop, condition is evaluated first and if it returns true then the statements inside while loop execute, this happens repeatedly until the condition returns false. When condition returns false, the control comes out of loop and jumps to the next statement in the program after while loop.
The important point to note when using while loop is that we need to use increment or decrement statement inside while loop so that the loop variable gets changed on each iteration, and at some point condition returns false. This way we can end the execution of while loop otherwise the loop would execute indefinitely. A while loop that never stops is said to be the infinite while loop, when we give the condition in such a way so that it never returns false, then the loops becomes infinite and repeats itself indefinitely.
Syntax for While Loop Statement in C++
while (condition) {
// body of the loop
}
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/* While Loop Statement in C++ language */
// program to find the sum of positive numbers
// if the user enters a negative number, the loop ends
// the negative number entered is not added to the sum
#include <iostream>
using namespace std;
int main() {
int number;
int sum = 0;
// take input from the user
cout << "Enter a number: ";
cin >> number;
while (number >= 0) {
// add all positive numbers
sum += number;
// take input again if the number is positive
cout << "Enter a number: ";
cin >> number;
}
// display the sum
cout << "\nThe sum is " << sum << endl;
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;
}
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;
}
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;
}
Standard end line (endl) in C++
A predefined object of the class called iostream class is used to insert the new line characters while flushing the stream is called endl in C++. This endl is similar to \n which performs the functionality of inserting new line characters but it does not flush the stream whereas endl does the job of inserting the new line characters while flushing the stream. Hence the statement cout<<endl; will be equal to the statement cout<< '\n' << flush; meaning the new line character used along with flush explicitly becomes equivalent to the endl statement in C++.
Syntax for end line (endl) in C++
cout<< statement to be executed <<endl;
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/* Standard end line (endl) in C++ language */
//The header file iostream is imported to enable us to use cout in the program
#include <iostream>
//a namespace called std is defined
using namespace std;
//main method is called
int main( )
{
//cout is used to output the statement
cout<< "Welcome to ";
//cout is used to output the statement along with endl to start the next statement in the new line and flush the output stream
cout<< "C#"<<endl;
//cout is used to output the statement along with endl to start the next statement in the new line and flush the output stream
cout<< "Learning is fun"<<endl;
}
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;
}
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;
}
Internal method to test if a positive number is prime. Not efficient algorithm. Using Internal method to return a prime number at least as large as n. Assumes "n > 0". Insert item x into
In C++ programming, you have to ask to the user to enter the desired decimal number to convert it into hexadecimal number to print the equivalent value in hexadecimal format
