for loop doubt

Question

#include <iostream>
using namespace std;

int main()
{
for (int a = 0; a < 6;a++) // if i put a++ here then i get output as 012345
{

cout << a << endl;
}

return 0;
}

#include <iostream>
using namespace std;

int main()
{
for (int a = 0; a < 6;) {

cout << a << endl;
a++; // if i put a++ here then i get no output
}

return 0;
}

#include <iostream>
using namespace std;

int main()
{
for (int a = 0; a < 6;) {
a++; // if here then i get 12345
cout << a << endl;

}

return 0;
}

please explain me how this loop is working and how i m getting different answers

thanks.

Answer 1

In the program given below, when a value becomes equal to 6, the condition fails so you will get 012345.

#include <iostream>
using namespace std;

int main()
{
for (int a = 0; a < 6;a++)
{

cout << a << endl;
}
return 0;
}

The code given below is same as that of above except, the increment operation is done inside the loop. This also results into the same answer as above. Here also you will get 012345. Just check once properly.

#include <iostream>
using namespace std;

int main()
{
for (int a = 0; a < 6;) {

cout << a << endl;
a++;
}

return 0;
}

In the last code, given below, the increment operation is done before the print operation, as a result 0 will not be printed and you will get the result 12345.

#include <iostream>
using namespace std;

int main()
{
for (int a = 0; a < 6;) {
a++;
cout << a << endl;

}

return 0;
}

Answer 2

after that if condition true it enters into loop after everything written inside loop block is compiled then compiler goes to increment and then checks condition
after that it goes inside loop if condition true
and this goes on

remember a compiler generally comes from top to bottom

Answer 3

u will understand all if u look into what compiler does
compiler first looks at initialisation like int I=0
then it checks condition like I<10

Answer 4

for loop always works in such a fashion that the initialization takes place then the condition is checked then it will perform the function in it.then only it consider the increment or decrement.but in the 3 rd one u have the increment as a function inside the loop.hence it prints12345

Answer 5

#include <iostream>
using namespace std;

int main()
{
for (int a = 0; a < 6;a++)
{

cout << a << endl;
}
return 0;
}

why 012345 is coming ? initally a = 0 then increment of a that is a++ is taking place before printing so it should only print 12345
why 0 is coming
and when does compiler increment ?

Answer 6

you mean after checking for the condition compiler first prints the value then increment takes place then again it checks for the condition and prints then increments and so on until condition fails...
thanks bro..

Answer 7

The last code should output 123456

Answer 8

for loop .work whenever expression is true.but 0 equality false. so there nothing to do in blacket.