minimal.tex

% This is the excerpt from plain TeX format
% that contains minimal instructions to just print "Hello \TeX".

% catcode definitions
\catcode`\{=1 % left brace is begin-group character
\catcode`\}=2 % right brace is end-group character
\catcode`\$=3 % dollar sign is math shift
\catcode`\&=4 % ampersand is alignment tab
\catcode`\#=6 % hash mark is macro parameter character
\catcode`\^=7 \catcode`\^^K=7 % circumflex and uparrow are for superscripts
\catcode`\_=8 \catcode`\^^A=8 % underline and downarrow are for subscripts
\catcode`\^^I=10 % ascii tab is a blank space

% We make @ signs act like letters, temporarily, to avoid conflict
% between user names and internal control sequences of plain format.
\catcode`@=11

% Assign initial values to TeX's parameters
\hsize=6.5in
\vsize=8.9in
\parfillskip=0pt plus 1fil

% Definitions for preloaded fonts
\font\tenrm=cmr10 % roman text

% Macros for setting ordinary text
\def\TeX{T\kern-.1667em\lower.5ex\hbox{E}\kern-.125emX}

% Initial values for standard layout
\tenrm % select roman font

% Main content
Hello \TeX

\end