how CAD calculated a length

I am not looking for the command. I want to know how CAD measures the distance between 2 points. which algorithm does the CAD code uses to measure the distance between 2 points produced from some object intersections?

probably standard geometry relationships/formulas.

say you have p1 with coordinates x1,y1,z1

the distance between p1 and p2 is

((x2^2-x1^2)+((y2^2-y1^2)+(z2^2-z1^2))^0.5

the case is not just having 2 obvious points p1& p2. imagine in a complex drawing with circles, triangles and lines intersecting each other, CAD can give you the distance between each random intersecting points, I do not think it calculates coordinates of all intersecting points.

Every AutoCAD object it is derived from a base object.

For what I know about Custom Objects, you can define the osnaps points for each of your objects, then that can be read by many of the built-in commands or functions.

I do not think it calculates coordinates of all intersecting points.

That's not such a difficult thing to do