To plot lines or points in lo-res:
Points:
PLOT x,y
Lines:
PLOT w,x TO y,z
w,x,y,z=0-39
You can't do that. You can only do:
HLIN x1, x2 AT y
or
VLIN y1, y2 AT x
And if you POKE 49234,1 you will get a full 40x48 screen of graphics. Do
POKE 49235,1 to get the four-line text window back. There are a number of
other "soft switch" locations. POKE 49236,1 selects graphics page 1 and POKE
49237,1 selects page 2. The last two are most useful in high-res mode,
because low-res page 2 is the default starting location for BASIC programs.
Incidentally, low-res and text modes use the same memory locations but
interpret them differently. So of course there is a text page 2 but you
still have to move your program to use it (just as with low-res page 2).
To get into the monitor:
CALL -151
L - list a section of memory (example: 300L)
G - executes instructions (example: 300G)
To get out of the monitor:
Ctrl-C Return - return to BASIC
There are, of course, many other features in the ROM; it's just a matter of
digging up the programming info. And (since you have such a late member of
the ][ series) there are also features in the hardware, such as double-
resolution text, low-res, and high-res modes, that the ROM was never updated
to handle. However, you might try
PR#3
and see if you get 80-column mode.
-- Derek