Re: Double lowres graphics?

[dempson@actrix.gen.nz (David Empson)]

Dennis Jenkins <dennis@usb.com> wrote:

> How to I programmatically turn on and off the 80 column firmware such that
> the output routine at $FDED will understand what I'm doing?  I know I can
> turn it on with a "jsr $c300", but how do I turn it off?

If you are doing this from BASIC, the correct way to control the
80-column firmware are as follows.

To enable the 80-column firmware and start 80-column mode:

    PRINT CHR$(4);"PR#3"

Once the 80-column firmware is active, to switch to 40-column mode while
leaving the 80-column firmware active:

    PRINT CHR$(17);

Once the 80-column firmware is active, to switch to 80-column mode:

    PRINT CHR$(18);

To switch off the 80-column firmware and return to 40-column mode:

    PRINT CHR$(21);


These should also work in machine code, except that you will have to
deal with BASIC.SYSTEM interaction (unless you are writing a SYS file).