The editor internally supports a set of Cntrl+alphabet's. But to avoid the awkward pressing of the Cntrl key, a zero'th column(text column number 1 starts at physical column 2) is reserved for single-pressing commands.
So externally the editor is also supported by a corresponding set of software robots. By incorporating robotic features in the I/O routines, these fixed external robots and the ones generated as recordings of actual editting processes make it possible to provide a full set of single-pressing commands in column zero.
The editor is thus separated into a single-pressing command mode and a full-screen editting mode. In the command mode, pressing of any alphabet would execute an external robot, which for now is just set to be the equivalent Cntrl+alphabet command.
The built-in robotic capability lends itself to easy construction of macro series of commands, or vanpool commands. This feature of vanpool commands could be used in the future to expand the capabilities of the single-pressing commands in column zero.
But once the cursor is moved out of column zero, any thing typed are registered(replacing the existing text). The [Del] and [Ins] key are used, what else, for delete and insert characters, respectively.
In column zero the [Del] and [Ins] keys are use to delete and insert a block of text, formed by [Home] and [End] keys. This left the [Backspace] key for deleting the current statement.
3.5
HOW TO EDIT
3.6
DIAGNOSIS HOW-TO