problem with boolean

[abc++]

Hi, I wrote this code but why writing 0 it print true instead of false?
Thanks!

#include <iostream>
int main ()
{
bool a;
std::cout << "insert 0 or 1:";
std::cin >> a;
if (a=true)
{
std::cout << "a is true";
}
else
{
std::cout << "a is false";
}

}