136 0 and a fixed number (say 100). Take the grammar of this language from the lectures. As another 

   136 0 and a fixed number (say 100). A partial grammar of the WHILE language is given below. 

   137 guidance have a look at the Fibonacci program

   137 

   138 and ``three-nested-loops'' program shown below. For example, printing a variable \texttt{x} in the 

   138 \begin{center}

   139 WHILE language can be done by using the command \mbox{\texttt{write x}}. 

   139 \begin{tabular}{@{}lcl@{}}

   140 \textit{Stmt} & $\rightarrow$ &  $\texttt{skip}$\\

   141               & $|$ & \textit{Id}\;\texttt{:=}\;\textit{AExp}\\

   142               & $|$ & \texttt{if}\; \textit{BExp} \;\texttt{then}\; \textit{Block} \;\texttt{else}\; \textit{Block}\\

   143               & $|$ & \texttt{while}\; \textit{BExp} \;\texttt{do}\; \textit{Block}\\

   144               & $|$ & \texttt{read}\;\textit{Id}\\

   145               & $|$ & \texttt{write}\;\textit{Id}\\

   146               & $|$ & \texttt{write}\;\textit{String}\medskip\\

   147 \textit{Stmts} & $\rightarrow$ &  \textit{Stmt} \;\texttt{;}\; \textit{Stmts}\\

   148               & $|$ & \textit{Stmt}\medskip\\

   149 \textit{Block} & $\rightarrow$ &  \texttt{\{}\,\textit{Stmts}\,\texttt{\}}\\

   150                 & $|$ & \textit{Stmt}\medskip\\

   151 \textit{AExp} & $\rightarrow$ & \ldots\\

   152 \textit{BExp} & $\rightarrow$ & \ldots\\

   153 \end{tabular}

   154 \end{center}

   155 

   156 \noindent

   157 As another guidance for your program have a look at the Fibonacci program

   158 and ``three-nested-loops'' program shown below in Figures \ref{fib} and \ref{loop}. 

   159