Before we go any further, we will need a few notational conventions, so
let us introduce some. We use underlined type for things that you
will type. We use typewriter
for labels and prompts, such as the
prompt in the PDP++ shell or a label on a type-in menu boxes. bold
is used to denote an object type name, like BpUnit. We use
italic for menu items or buttons you will click on or select using
the SELECT (usually left) mouse key. For multi-step menu selections we
will use statements like 'select A/B/C'. This means that you should
press and hold the select key on menu item A. When a popup menu
appears move the pointer to item B. When a further popup menu
appears, move the pointer to C, and then release the select key.
Finally, we use double quotes to designate strings that name objects
such as files, layers, units, etc.