Enter Edit Mode by pressing Alt+E.  In Edit Mode, text that you type will
be written into the current page buffer.  When typing, the cursor will advance
in the direction in which it was last moved by the arrow keys.

When finished editing, press Alt+S to save the changed page to disk and
exit Edit Mode; or press Alt+L to reload the page from the disk, abandon any
edits, and exit Edit Mode.  Some commands only work in Edit Mode; these are:

    Alt+V (paste page)           Alt+H (toggle high bit)
    Alt+P (paste byte)           Alt+F (fill page with byte under cursor)
    Alt+X (cut page)
    Ctrl+Left (decrement byte)   Ctrl+Right (increment byte)

PgUp and PgDown move between pages.  Alt+G allows you to type in a page number
and jump to it; Alt+J jumps to a page number underneath the cursor.

Alt+R treats the page as a machine-language program (a "binary" executable) and
runs it.  If the screen becomes garbled, F5 will refresh the status bar lights.
Alt+M will show more page (less status bar) and Alt+N will show less page.