\def\makeatother{\catcode`\@=12}
\def\makeatletter{\catcode`\@=11}
\font\tt=psmcoub

%%%%  Use \begintt .... \endtt
%%%%  explicit composing remarks have | as escape character

\newskip\ttglue

\ttglue=0.5em plus 0.25em minus 0.15em


\chardef\other=12
\outer\def\ttverbatim{\begingroup \catcode`\\=\other \catcode`\{=\other
  \catcode`\}=\other \catcode`\$=\other \catcode`\&=\other 
  \catcode`\#=\other \catcode`\%=\other \catcode`\~=\other 
  \catcode`\_=\other \catcode`\^=\other 
  \obeyspaces\obeylines\tt}
{\obeyspaces\gdef {\ }} % \obeyspaces now gives \ , not \space
\def\begintt{\smallskip\let\par=\endgraf \ttverbatim \parskip=3pt
  \catcode`\|=0 \leftskip=0pc \ttfinish}
{\catcode`\|=0 \catcode`|\=\other %| is temporary escape character
  |obeylines  % End of line is active
  |gdef|ttfinish#1^^M#2\endtt{#1#2|smallskip|endgroup}}
\catcode`\|=\active
{\obeylines\gdef|{\ttverbatim\spaceskip=\ttglue\let^^M=\ \let|=\endgroup}}

.