Bucles en C y C++

En programación, a veces es necesario realizar alguna operación más de una vez o (digamos) n número de veces. Los bucles se utilizan cuando necesitamos ejecutar repetidamente un bloque de instrucciones. 

Por ejemplo : supongamos que queremos imprimir «Hello World» 10 veces. Esto se puede hacer de dos maneras como se muestra a continuación: 

// C program to illustrate need of loops
#include <stdio.h>
 
int main()
{
    printf( "Hello World\n");
    printf( "Hello World\n");
    printf( "Hello World\n");
    printf( "Hello World\n");
    printf( "Hello World\n");
    printf( "Hello World\n");
    printf( "Hello World\n");
    printf( "Hello World\n");
    printf( "Hello World\n");
    printf( "Hello World\n");
     
    return 0;
}

// C++ program to illustrate need of loops
#include <iostream>
using namespace std;
 
int main()
{
    cout << "Hello World\n";
    cout << "Hello World\n";
    cout << "Hello World\n";
    cout << "Hello World\n";
    cout << "Hello World\n";
    cout << "Hello World\n";
    cout << "Hello World\n";
    cout << "Hello World\n";
    cout << "Hello World\n";
    cout << "Hello World\n";
    return 0;
}

// C program to illustrate for loop
#include <stdio.h>
 
int main()
{
    int i=0;
     
    for (i = 1; i <= 10; i++)
    {
        printf( "Hello World\n");   
    }
 
    return 0;
}

// C++ program to illustrate for loop
#include <iostream>
using namespace std;
 
int main()
{
    for (int i = 1; i <= 10; i++)
    {
        cout << "Hello World\n";
    }
 
    return 0;
}

// C program to illustrate while loop
#include <stdio.h>
 
int main()
{
    // initialization expression
    int i = 1;
 
    // test expression
    while (i < 6)
    {
        printf( "Hello World\n");   
 
        // update expression
        i++;
    }
 
    return 0;
}

// C++ program to illustrate while loop
#include <iostream>
using namespace std;
 
int main()
{
    // initialization expression
    int i = 1;
 
    // test expression
    while (i < 6)
    {
        cout << "Hello World\n";
 
        // update expression
        i++;
    }
 
    return 0;
}

// C program to illustrate do-while loop
#include <stdio.h>
 
int main()
{
    int i = 2; // Initialization expression
 
    do
    {
        // loop body
        printf( "Hello World\n");   
 
        // update expression
        i++;
 
    }  while (i < 1);   // test expression
 
    return 0;
}

// C++ program to illustrate do-while loop
#include <iostream>
using namespace std;
 
int main()
{
    int i = 2; // Initialization expression
 
    do
    {
        // loop body
        cout << "Hello World\n";
 
        // update expression
        i++;
 
    }  while (i < 1);   // test expression
 
    return 0;
}

// C program to demonstrate infinite loops
// using for and while
// Uncomment the  sections to see the output
 
#include <stdio.h>
 
int main ()
{
    int i;
 
    // This is an infinite for loop as the condition
    // expression is blank
    for ( ; ; )
    {
       printf("This loop will run forever.\n");
    }
 
    // This is an infinite for loop as the condition
    // given in while loop will keep repeating infinitely
    /*
    while (i != 0)
    {
        i-- ;
        printf( "This loop will run forever.\n");
    }
    */
 
    // This is an infinite for loop as the condition
    // given in while loop is "true"
    /*
    while (true)
    {
        printf( "This loop will run forever.\n");
    }
    */
}

// C++ program to demonstrate infinite loops
// using for and while
// Uncomment the  sections to see the output
 
#include <iostream>
using namespace std;
int main ()
{
    int i;
 
    // This is an infinite for loop as the condition
    // expression is blank
    for ( ; ; )
    {
        cout << "This loop will run forever.\n";
    }
 
    // This is an infinite for loop as the condition
    // given in while loop will keep repeating infinitely
    /*
    while (i != 0)
    {
        i-- ;
        cout << "This loop will run forever.\n";
    }
    */
 
    // This is an infinite for loop as the condition
    // given in while loop is "true"
    /*
    while (true)
    {
        cout << "This loop will run forever.\n";
    }
    */
}

#include <stdio.h>
 
int main() {
 
    while (1)
        printf("This loop will run forever.\n");
    return 0;
}

#include <iostream>
using namespace std;
 
int main()
{
 
    while (1)
        cout << "This loop will run forever.\n";
    return 0;
}

#include <stdio.h>
 
int main() {
 
    do{
        printf("This loop will run forever.\n");
    }
      while(1);
    return 0;
}

#include <iostream>
using namespace std;
 
int main() {
  
    do{
        cout << "This loop will run forever.\n";
    } while(1);
  
    return 0;
}