Added semester notes.

src/op/system/definitions.tex

@@ -0,0 +1,9 @@
+\section{Operator Systems}
+\label{section:operator-systems}
+
+\begin{definition}[Operator System]
+\label{definition:operator-system}
+    Let $A$ be a $C^*$-algebra and $S \subset A$, then $S$ is an \textbf{operator system} if $S$ is a linear subspace of $A$ and $S = S^*$. 
+\end{definition}
+
+

src/op/system/index.tex

@@ -0,0 +1,4 @@
+\chapter{Operator Systems}
+\label{chap:opertaor-systems}
+
+\input{./definitions.tex}