# Confusion regarding notation/symbol?

I was reading circular convolution topic from Digital Signal Processing Using Matlab 3rd Ed,by Proakis. I came across a strange term/symbol; I have highlighted it in attached snapshot

Update:Pg150; same chapter,same book(just before example 5.4) contains this notation and mentions that it is a rectangular window of length N

I have also attached snap of eq 5.24,in 2nd snap, where this RN(n) symbol appears also:  • Can you give a little more context on the topic being explained here? By looking at just this I can only imagine that this term represents $n^{th}$ component of a Vector in N dimension, usually represented as $\mathcal{R}^N$ Jun 20, 2020 at 11:44
• Proakis / edited multiple books, in multiple revisions. Which one is this, which page? Jun 20, 2020 at 11:53

This symbol denotes a rectangular pulse of length $$N$$:
$$\mathcal{R}_N(n)=\begin{cases}1,&0\le n\le N-1\\0,&\textrm{otherwise}\end{cases}$$
I'm not sure where it is defined for the first time, but this definition is clear from the equation above Eq. $$(5.24)$$ on page $$130$$ of the 3rd edition of Digital Signal Processing Using Matlab by V.K. Ingle and J.G. Proakis.
• @engr: I don't see how it's different. If you interpret $\mathcal{R}_N(n)$ as in my answer, it matches exactly the equation given in the book. Jun 20, 2020 at 14:49