How to Convert Decimal to Binary in C++
- Use Custom Defined Function to Convert Decimal Number to Binary in C++
-
Use
std::bitsetClass to Convert Decimal Number to Binary in C++
This article will introduce several methods of how to convert decimal numbers to binary representation in C++.
Use Custom Defined Function to Convert Decimal Number to Binary in C++
The flexible method defines a function that takes the int value, converts it to corresponding binary representation, and returns it as a string value. In this case, we implemented the algorithm using modulo % operator and while loop, where we decrease the value of integer by half each iteration.
#include <iostream>
using std::cout;
using std::endl;
using std::string;
string toBinary(int n) {
string r;
while (n != 0) {
r += (n % 2 == 0 ? "0" : "1");
n /= 2;
}
return r;
}
int main() {
int number = 15;
cout << "decimal: " << number << endl;
cout << "binary : " << toBinary(number) << endl;
return EXIT_SUCCESS;
}
Output:
decimal: 15
binary : 1111
Use std::bitset Class to Convert Decimal Number to Binary in C++
Alternatively, we can directly use the bitset class from the STL library. bitset represents a fixed-size sequence of N bits, and it offers multiple built-in methods to manipulate the binary data efficiently. The following example shows the bitset object construction by passing the string value and an int value.
#include <bitset>
#include <iostream>
using std::bitset;
using std::cout;
using std::endl;
using std::string;
string toBinary(int n) {
string r;
while (n != 0) {
r += (n % 2 == 0 ? "0" : "1");
n /= 2;
}
return r;
}
int main() {
int number = 15;
bitset<32> bs1(toBinary(number));
cout << "binary: " << bs1 << endl;
bitset<32> bs2(number);
cout << "binary: " << bs2 << endl;
return EXIT_SUCCESS;
}
Output:
binary: 00000000000000000000000000001111
binary: 00000000000000000000000000001111
Notice that we specified 32 bits to be allocated during the bitset declaration in the previous code. We can specify a different number of bits to suit their needs better. Multiple scenarios are demonstrated in the following code segment:
#include <bitset>
#include <iostream>
using std::bitset;
using std::cout;
using std::endl;
using std::string;
int main() {
int number = 15;
bitset<32> bs1(number);
cout << "binary: " << bs1 << endl;
bitset<16> bs2(number);
cout << "binary: " << bs2 << endl;
bitset<8> bs3(number);
cout << "binary: " << bs3 << endl;
bitset<5> bs4(number);
cout << "binary: " << bs4 << endl;
cout << endl;
return EXIT_SUCCESS;
}
Output:
binary: 00000000000000000000000000001111
binary: 0000000000001111
binary: 00001111
binary: 01111
bitset class has several useful methods to operate on its content. These methods can be employed to invert all bits of the set (flip function) or to reset/set the specified bits in the sequence. The core binary operations like AND, OR, XOR, NOT and SHIFT are also supported. We show a couple of them in the example below, but you can see the full manual of the bitset class here.
#include <bitset>
#include <iostream>
using std::bitset;
using std::cout;
using std::endl;
using std::string;
int main() {
int number = 15;
bitset<32> bs(number);
cout << "binary : " << bs << endl;
cout << "flipped: " << bs.flip() << endl;
cout << "shift>4: " << (bs >>= 6) << endl;
cout << "shift<5: " << (bs << 2) << endl;
cout << "reset : " << bs.reset() << endl;
cout << "set : " << bs.set(16) << endl;
return EXIT_SUCCESS;
}
Output:
binary : 00000000000000000000000000001111
flipped: 11111111111111111111111111110000
shift>4: 00000011111111111111111111111111
shift<5: 00001111111111111111111111111100
reset : 00000000000000000000000000000000
set : 00000000000000010000000000000000
Founder of DelftStack.com. Jinku has worked in the robotics and automotive industries for over 8 years. He sharpened his coding skills when he needed to do the automatic testing, data collection from remote servers and report creation from the endurance test. He is from an electrical/electronics engineering background but has expanded his interest to embedded electronics, embedded programming and front-/back-end programming.
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