f                   n1 .. n2
Compute the function f at x=n1, and
leave the result as n2. This word
defines the function that is used for
plotting and finding zeroes.
initialize

newx                   .. n1
internal variable used in plotting

newy                   .. n1
internal variable used in plotting

oldx                   .. n1
internal variable used in plotting

oldy                   .. n1
internal variable used in plotting

plotAxes
puts the screen in graphics mode and
draws axes at positions derived from
the values of xmin,xmax,ymin and ymax

plotf         n1 n2 n3 ..
show a plot of the function defined in
word "f" from x=n1 to x=n2 in steps of
n3. Draws axes where appropriate.
The y scale should be set up first by
assigning values to ymin and ymax.
Push any key to return to BCL after the
plot is completed.

rline            n1 n2 ..
draw a line from the previous position
(contained in oldx,oldy) to the
position x=n1, y=n2. Update oldx and
oldy.

scaleX              n1 .. n2
calculate the screen X-position of
n1 and leave it as n2. Use xmin,
xmax, scrXmin and scrXmax

scaleY              n1 .. n2
calculate the screen Y-position of
n1 and leave it as n2. Use ymin,
ymax, scrYmin and scrYmax

scrXmax                .. n1
constant which defines the highest
x-coordinate on the screen (=239)

scrXmin                .. n1
constant which defines the lowest
x-coordinate on the screen (=0)

scrYmax                .. n1
constant which defines the highest
y-coordinate on the screen (=0)

scrYmin                .. n1
constant which defines the lowest
y-coordinate on the screen (=63)

x                      .. n1
Internal running variable of plotf and
zerof

xmax                   .. n1
Internal variable which defines the
interval of the function "f" for
which the plotting or zero search is
being carried out

xmin                   .. n1
Internal variable which defines the
interval of the function "f" for which
the plotting or zero search is being
carried out

xstep                  .. n1
Internal variable which defines the
minimum step with which plotting or
zero searching is to be carried out

ymax                   .. n1
Defines the maximum value of "f" which
should be displayed on the screen when
plotting.
Also used as internal variable for
zero finding; therefore looses it's
value after "zerof"

ymin                   .. n1
Defines the minimum value of "f" which
should be displayed on the screen when
plotting
Also used as internal variable for
zero finding; therefore looses it's
value after "zerof"

zerof         n1 n2 n3 .. n4
Find a zero of the function defined in
word "f" in the interval x=n1 to x=n2.
The required accuracy is equal to or
better than n3. Leave the result as n4.
There should be exactly one zero in the
interval n1..n2. The algorithm used is
the interval halving algorithm.
Subsequent estimates for the zero are
displayed.