diff --git a/docs/document.tex b/docs/document.tex
index ab9c5b5..a56f919 100644
--- a/docs/document.tex
+++ b/docs/document.tex
@@ -9,6 +9,7 @@
 	\tableofcontents
 	\chapter{Overview}
 	\section{Introduction}
+	This is a very poorly thought out 16-bit machine, but you've got to start somewhere. Currently debating between a CPU status register, 80x86 style, or just placing arithmetic results into a predetermined register.
 	\section{Registers}
 	The following are the general purpose registers that can be used.
 	\begin{itemize}
@@ -36,6 +37,55 @@
 		\caption{Memory Layout}
 	\end{figure}
 	\chapter{ISA}
+	\section{Instruction Encoding}
+	Instructions are fixed to one byte in length. For instructions that can take a register as their first or second operand the 3 least significant bits are set 
+	to indicate the register file to use. So an instruction with format XXXX X000 will use Register 1 and so forth all the way to the pattern XXXX X111, which will be Register 8.
+	In instances where the second operand may be one of three options bits 4 and 5 are set as shown below:\\\\
+	\begin{tabular}{ c c }
+		\hline
+		Bit Pattern & Type \\
+		\hline
+		XXX0 0XXX & Register \\
+		XXX0 1XXX & Constant \\
+		XXX1 0XXX & Address \\
+		\hline
+	\end{tabular}
 	\section{COPY}
+	\begin{tabular}{ c c c c }
+		\hline
+		Opcode & Mnemonic & Operand 1 & Operand 2 \\
+		\hline\hline
+		0x20 & COPY & Register & Immediate 16 / Address, Register \\
+		0xA0 & COPY & Address & Immediate 16 / Address, Register \\
+		\hline
+	\end{tabular}\\[6pt]
+	Copies 2 bytes of data from either a memory address, a runtime constant or a CPU register into either another CPU register or a memory location.
 	\section{CMP}
+	\begin{tabular}{ c c c c }
+		\hline
+		Opcode & Mnemonic & Operand 1 & Operand 2 \\
+		\hline\hline
+		0x80 & CMP & Register & Register, Immediate 16 / Address \\
+		\hline
+	\end{tabular}\\[6pt]
+	Compares two values and sets a CPU status flag (maybe...).
+	\section{ADD}
+		\begin{tabular}{ c c c c }
+		\hline
+		Opcode & Mnemonic & Operand 1 & Operand 2 \\
+		\hline\hline
+		0x40 & ADD & Register & Register, Immediate 16 \\
+		\hline
+	\end{tabular}\\[6pt]
+	Performs addition on a register with a value from another (or the same) register or a runtime constant.
+	\section{SUB}
+	\begin{tabular}{ c c c c }
+		\hline
+		Opcode & Mnemonic & Operand 1 & Operand 2 \\
+		\hline\hline
+		0x60 & SUB & Register & Register, Immediate 16 \\
+		\hline
+	\end{tabular}\\[6pt]
+	Performs subtraction on a register with a value from another (or the same) register or a runtime constant.
+
 \end{document}