data w
read x1 2
read y1 3
read x2 4
read y2 5
set dx = x2-x1
set dy = y2-y1
device xterm
lim dx dy
box
points dx dy
limits x1 dx
erase
box
points x1 dx
limits x1 -.001 .001
erase
box
points x1 dx
data w
history
limi x1 y1
limits x1 y1
erase
box
points x1 y1
limits dx dy
erase
box
points dx dy
 set dx = x2-x1
 set dy = y2-y1
limits dx dy
erase
box
limits x1 dx
erase
box
points x1 dx
limits y1 dy
erase
box
points y1 dy
limits dx dy
erase
box
points dx dy
quit
