grread

(grread  [track]  [allkeys  [cursortype]])

The input argument 'allkeys' supports an additional bit flag value compared to standard AutoLISP :

Bit 7 (= 128) : return extended keyboard keycodes
allows to instructs (grread) to also report those keyboard codes, not provided by standard AutoLISP, for these following keys 

all 4 cursor keys, Insert, Delete, Home, End, PageUp, PageDown

Using the extra bit flag allows existing Lisp functions to maintain compatibility with standard AutoLISP, but to take advantage of BricsCAD, when using the additional flag; fortunately, AutoCAD ignores the "128" bit value.