A car with a shock will typically have an upper arm. A vehicle with i-beam or twin i-beam front suspension is an obvious exception
A car with a strut will not have an upper arm
A strut is attached to the the steering knuckle. It is, in a way, part of the car’s steering system
a shock will typically be attached to the lower arm. A vehicle with i-beam or twin i-beam front suspension is an obvious exception. A shock is not truly part of the car’s steering system
not all struts are coil-over, by the way
“modified mcpherson strut” has the coil next to the strut. Benz and Ford come to mind
Another thing - MacPherson was a U.S. Chevy engineer when he invented it for use in Chevy’s “Cadet” post WW2 (1946) compact car, which wasn’t produced. He then moved to Ford, which used it in European models starting in 1950.
As already described, a strut controls the movement of the steering knuckle (front) or hub (rear) as it moves through its suspension and steering movement. A coilover shock is simply a damper with the coil spring wrapped around it, and it does not control the movement of the steering and/or suspension. On an earlier page I posted a drawing of my car’s rear end. Those are coilover shocks. The shocks and springs come out as assemblies, but the movement of the hub is controlled by the upper and lower control arms.
Disconnect a strut from the steering knuckle and the knuckle will hang free (unless you stack a hanger it’ll hang on the brake line… a definite no-no). Disconnect a coilover shock from its steering knuckle (lower A-frame or control arm) and the knuckle will still be held in its proper place by the other steering and suspension components.