#030 – Printing integers in binary

Consider the following:

#include <iostream>

int main()
{
	int bin {};
    bin = 0b0011; // Assign binary 3 to the variable
    std::cout << bin << '\\n' // Prints decimal 3
    
    bin = 0b1100;
    std::cout << bin << '\\n'; // Prints decimal 12
}

// Terminal
3
12

Hey! What happened?

We assigned binary values to the variable however std::cout printed their decimal representation.

C++ allows us to initialize a variable with any numbering system

int a { 12 };
int b { 0b1100 };
int c { 0xC };

All of these values are equivalent. However, the variable doesn’t record if its decimal, hexadecimal, binary or octal.

How std::cout behaves

std::cout defaults to printing decimal. It can be formatted to support other number systems via std::hex, std::oct. However, it doesn’t support the binary system.

Aah. Printing binary is more cumbersome

The solution is to use <bitset>.

The program below prints numbers which are of type std::bitset. A helper function is used to add whitespace for long binary numbers. This is to enhance readability as 1100111001010001 is quite difficult to discern.

#include <iostream>
#include <bitset>
#include <string>

std::string addNibbleSpacing(std::string bits)
{
    std::string formatted{};

    for (std::size_t i{0}; i < bits.length(); ++i)
    {
        formatted += bits[i];

        if ((i + 1) % 4 == 0 && i + 1 != bits.length())
        {
            formatted += ' ';
        }
    }
    return formatted;
}

int main()
{
    std::bitset<8> b1 { 0b1101'0010 };
    std::bitset<16> b2 { 0b1100'1110'0101'0001 };

    std::cout << "The binary values are:\\n";
    std::cout << "8-bit value:  " << addNibbleSpacing(b1.to_string()) << '\\n';
    std::cout << "16-bit value: " << addNibbleSpacing(b2.to_string()) << '\\n';
}

// Output
The binary values are:
8-bit value:  1101 0010
16-bit value: 1100 1110 0101 0001