Writing numbers in binary notation means expressing them as a sequence of binary digits (bits), either 0 or 1. Each number must be represented by powers of two. Counting from the left, the position represents the exponent of this power.

For example, in binary, we can write the number 155 into powers of two, as shown below:

$155\phantom{\rule[-0.0ex]{0.0em}{0.0ex}}\phantom{\rule[-0.0ex]{0.0em}{0.0ex}}equals;{128}plus;{16}{plus;}{8}plus;{2}{plus;}{1}\phantom{\rule[-0.0ex]{0.0em}{0.0ex}}\phantom{\rule[-0.0ex]{0.0em}{0.0ex}}\phantom{\rule[-0.0ex]{0.0em}{0.0ex}}equals;{}{{2}}^{{7}}plus;{{2}}^{{4}}plus;{{2}}^{{3}}plus;{{2}}^{{1}}plus;{{2}}^{{0}}\phantom{\rule[-0.0ex]{0.0em}{0.0ex}}\phantom{\rule[-0.0ex]{0.0em}{0.0ex}}\phantom{\rule[-0.0ex]{0.0em}{0.0ex}}\phantom{\rule[-0.0ex]{0.0em}{0.0ex}}equals;{1}{\cdot}{{2}}^{{7}}plus;0\cdot {2}^{6}plus;0\cdot {2}^{5}plus;{1}{\cdot}{{2}}^{{4}}{plus;}{1}{\cdot}{{2}}^{{3}}plus;0\cdot {2}^{2}plus;{1}{\cdot}{{2}}^{{1}}plus;{1}{\cdot}{{2}}^{{0}}\phantom{\rule[-0.0ex]{0.0em}{0.0ex}}\phantom{\rule[-0.0ex]{0.0em}{0.0ex}}\phantom{\rule[-0.0ex]{0.0em}{0.0ex}}equals;{1}00{1}{1}0{1}{1}$(in binary)