PLDdiagrams.tex

\usepackage{tikz}
\usetikzlibrary{calc}

% ...

\newcommand{\Compiler}[4]{
  \draw (#1) -- ++(3, 0) -- ++(0, -1) -- ++(-1, 0)
  -- ++(0, -1) -- ++(-1, 0) -- ++(0, 1)
  -- ++(-1, 0) -- ++(0, 1);
 \node at ($(#1)+(0.5, -0.5)$) {\Large #2};
 \node at ($(#1)+(2.5, -0.5)$) {\Large #4};
 \node at ($(#1)+(1.5, -1.5)$) {\Large #3};
}

\newcommand{\Machine}[2]{
  \draw (#1) -- ++(1, 0) -- ++(-0.5, -1) -- ++(-0.5, 1);
  \node at ($(#1)+(0.5, -0.3)$) {#2};
}

\newcommand{\Program}[2]{
  \draw (#1) -- ++(0, -1) -- ++(1, 0) -- ++(0, 1);
  \draw (#1) [out=150,in=180] to ($(#1)+(0.5,1)$)x
  [in=25, out=0] to ($(#1)+(1,0)$);
  \node at ($(#1)+(0.5,-0.5)$) {\Large #2};
}

% ...

\begin{tikzpicture}
  \Compiler{1,1}{C}{C}{C}
  \Compiler{4,0}{C}{x86}{x86}
  \Machine{4,1}{x86}
  \Program{5,5}{C}
\end{tikzpicture}

Syntax error at the end of line #22: x should be ; instead.