Question

I’m a total beginner in C++ and today I thought I’d write myself a small program that converts a decimal number to binary. The code looked something like this:

#include <iostream>
void binaryConvert(int);
int main() {
    using namespace std;
    cout << "Enter decimal number for conversion:" << endl;
    int dec;
    cin >> dec;
    binaryConvert(dec);
}
void binaryConvert(int number) {
    using namespace std;
    while(number > 0) {
        int bin = number % 2;
        number /= 2;
        cout << bin;
    }
}

Logically, this program would print the binary the other way around. I spent a long time trying to figure out how to invert the order of the binary digits so that the binary number would appear the right way around when I came across this piece of code:

void binaryConvert(int number) {
    using namespace std;
    if(number > 0) {
        int bin = number % 2;
        number /= 2;
        binaryConvert(number);
        cout << bin;
    }
}

I know its probably a stupid question (I’m an absolute beginner), but I can’t figure out why this code prints the bits in the correct order. Also, how come the bits actually get printed if the function gets called again before cout even gets executed?

Answer 1

It utilizes recursion, the bin at the end will not be printed until the base case is hit (number <= 0) and then it will go up the stack trace.