Alternatively you can use an online tool like CyberChef
- Divide the base 10 number by 2 and store the remainder.
- Divide the quotient by 2 until the quotient is 0.
- Write the remainders in reverse to get the binary value.
42 / 2 = 21; 42 % 2 = 0
21 / 2 = 10; 21 % 2 = 1
10 / 2 = 5; 10 % 2 = 0
5 / 2 = 2; 5 % 2 = 1
2 / 2 = 1; 2 % 2 = 0
1 / 2 = 0; 1 % 2 = 1
Flag: picoCTF{101010}