You are spot on!
Try this code to see visually.
The white square is 100 units along each side and its centre is at 0,0,0
The yellow sphere is created as a 100 unit sphere. The unit is the diameter of the sphere. This is as you say, a sphere with a radius of 50 and defaults its centre as 0,0,0.
You can of course then move the object whereever you like and rotate them to desired angle.
sync on : sync rate 30 : autocam off
make object box 1,100,100,100 : ghost object on 1 : set object cull 1,0
make object sphere 2,100 : color object 2,rgb(255,255,0)
make object cube 3,100 : position object 3,200,0,0 : color object 3,rgb(128,0,0)
make object cube 4,100 : position object 4,0,200,0 : color object 4,rgb(0,128,0)
make object cube 5,100 : position object 5,0,0,200 : color object 5,rgb(0,0,128)
rem make axis
make object box 50,2000,5,5 : color object 50,rgb(255,0,0)
make object box 51,5,2000,5 : color object 51,rgb(0,255,0)
make object box 52,5,5,2000 : color object 52,rgb(0,0,255)
position camera 100,150,-400
do
rem rotate red box around x axis
xrotate object 3,wrapvalue(object angle x(3)+1)
rem rotate green box around y axis
yrotate object 4,wrapvalue(object angle y(4)+1)
rem rotate blue box around z axis
zrotate object 5,wrapvalue(object angle z(5)+1)
set cursor 0,0
print "X AXIS = RED"
print "Y AXIS = GREEN"
print "Z AXIS = BLUE"
sync
loop
Boo!
