The rectangular window is defined as a constant value of 1 over the entire window length and a value of 0 outside the window. $ w(n) = \begin{cases} 1 & 0 \leq n \lt M \\ 0 &\text{otherwise} \\ \end{cases}\\ $ It can also be expressed in terms of the [[discrete-time unit-step]]: $ w(n) = u(n) - u(n-M) $ ![[Window_function_and_frequency_response_-_Rectangular.svg]] [Wikimedia](https://en.wikipedia.org/wiki/File:Window_function_and_frequency_response_-_Rectangular.svg)