The Loop object is a loop or collection of coaxial loops. The Specs page of the edit window for a loop is a table of radius, altitude, and winding numbers for the loops. The table expands as you type more loops. Rows with missing radius will vanish from the table when you press the Set or Done buttons.
The wireDiameter box on the Supply page may be used to specify a wire radius to be used for all loops. Giving the wire a finite radius has two effects. Firstly, the wire is drawn with the specified thickness. Secondly, the field divergence associated with a filamentary conductor is avoided, since the field is calculated assuming uniform current density within the wire. BiotSavart uses a formula valid in the limit that the wire diameter is much smaller than the loop diameter.
Although the field due to the loop is calculated using Complete Elliptic Integrals, the loop is drawn using straight segments. The number of segments is set by the nPhi box on the Looks page. One can also specify a range of angles to draw, but keep in mind that the field is that of a whole loop! Quantities on the Looks page have no effect upon the calculated field.