$$$$

The syntax of the While Programming Language is given by the CFG with:

• Terminal symbols: $0,1,\dots ,9$, ${}^{\prime }$, $a,b,\dots ,z,A,B,\dots ,Z$, $\mathrm{\&}\mathrm{\&}$, $\Vert$, $!$, $+$, $\ast$, $-$, $\le$, $=$, $\leftarrow$, $;$.
• Nonterminal symbols: $S$, $B$, $A$, $D$, $E$, $L$, $U$, $M$, $V$, $N$

• Production rules:

  $$\begin{array}{rcl}S& ⟶& \mathsf{skip}\mid V\leftarrow A\mid S;S\mid \mathsf{if}B\mathsf{then}S\mathsf{else}S\mid \mathsf{while}B\mathsf{do}S\mid \{S\}\\ B& ⟶& \mathsf{true}\mid \mathsf{false}\mid A\le A\mid A=A\mid !B\mid B\mathrm{\&}\mathrm{\&}B\mid B\Vert B\mid (B)\\ A& ⟶& V\mid N\mid A+A\mid A-A\mid A\ast A\mid (A)\\ D& ⟶& 0\mid 1\mid \cdots \mid 9\\ E& ⟶& DE\mid ϵ\\ L& ⟶& a\mid b\mid \cdots \mid z\\ U& ⟶& A\mid B\mid \cdots \mid Z{\mid }^{\prime }\\ M& ⟶& LM\mid UM\mid ϵ\\ V& ⟶& LM\\ N& ⟶& DE\end{array}$$
• Start symbol: $S$