Binary number function - c++

Question

#include <iostream>
using namespace std;
void binary(unsigned a) {
int i;
cout << "0" << endl;
do {
for (i = 1; i < a; i=i/2) {
if ((a & i) != 0) {
cout << "1" << endl;
}
else {
cout << "0" << endl;
}
}
}
while (1 <= a && a <= 10);
}
int main(void) {
binary(4);
cout << endl;
}
I wrote a code about binary numbers. İt should give bits respect to entering number like for
4 (0100) for 2 (10). However my code goes infinity could you explain. I wrote in visual
studio and I cannot use <bits/stdc++.h> because there is no such a library in visual studio

Answer 1

Initially i is 1 but i = i / 2 sets i to 0, where it remains. The inner loop, therfore, loops for ever.
To output an unsigned number a in binary, use
#include <bitset>
#include <climits>
std::cout << std::bitset<sizeof(a) * CHAR_BIT>(a) << '\n';
(There is, at the time of writing no std::bin i/o manipulator cf. std::hex.)

Answer 2

Without using a built-in function, you can write your own function and perform your operation as follows.
Solution-1
#include <iostream>
void binary(unsigned int number)
{
if (number / 2 != 0) {
binary(number / 2);
}
std::cout << number % 2;
}
int main() {
binary(10);
}
Solution-2
#include <iostream>
#include<string>
void binary(unsigned int number)
{
std::string str = "";
while (number != 0) {
str = (number % 2 == 0 ? "0" : "1") + str;
number /= 2;
}
std::cout << str;
}
int main()
{
binary(4);
}
Note : Don't use using namespace std; . Why is "using namespace std;" considered bad practice?