One of the first things people tend to do with ET is
create new Tcl/Tk commands, written in C, that do computations that
are either too slow or impossible with a pure Tcl.
This is a two-step process.
First you have to write the C code using the ET_PROC
construct.
Then you have to register your new Tcl/Tk command with the Tcl/Tk
interpreter using the ET_INSTALL_COMMANDS
statement.
We will consider each of these steps in turn.