option nolet
declare function f
! divide window in two equal parts
open #1:screen 0,0.5,0,1  ! window #1
open #2:screen 0.5,1,0,1  ! window #2
!open #N:left,right,bottom,top
! window closed: closed #N, N positiv integer.
!=> make window #1 active
window #1
call info(a)
clear  ! window clear contens #1,removed info(a)
window #2
! tab used to print txt logical window
print tab (5);"window2"
print
ask max cursor r2,c2
print " r2:number of rows     window #2";r2
print " c2:number of columns  window #2";c2
open #3:screen 0.5,1,0,0.5  ! window #3
set window -6.283,6.283,-1.1,1.1
window #3
print tab(5);"window3,draw :sin(x)"
print
ask max cursor r3,c3
print " r3:number of rows     window #3";r3
print " c3:number of columns  window #3";c3
! draw : y=sin(x)
function f(x) = sin(x)
x_step =.002
for x=-5 to 5 step x_step
      set color "red" 
      y=sin(x)
      plot x,y
next x
! draw :title
set color "blue"
print tab(5,10);" function to draw : y = sin(x) "
! draw :coordinate axis
set color "green"
plot lines :-5,0;5,0  ! x axis
plot lines :0,-1;0,1  ! y axis
print
print " user :coordinaat system, ask window xl,xr,yb,yt "
print
ask window xmin,xmax,ymin,ymax
print " xmin(=xl) = ";xmin
print " xmax(=xr) = ";xmax
print " ymin(=yb) = ";ymin
print " ymax(=yt) = ";ymax
window #1
set color "black"
print
call info(a)
print
print tab(5);"window1"
print
ask max cursor r1,c1
print " r1:number of rows     window #1";r1
print " c1:number of columns  window #1";c1
!******************************************************
! three logical windows , window #1,window #2,window #3
!******************************************************
end

sub info(a)
print tab(7); "*********************************************"
print tab(7); "* prog : divide window , version 1.0        *"
print tab(7); "* peter.vlasschaert@gmail.com,29/02/2020    *"
print tab(7); "*********************************************"
end sub