not igef; IGES is a widely-used interchange format that supports points, lines, arcs, splines and surfaces, but it's not parametric.
Parasolid and Step are the two most widely used parametric formats. That means that one can ascribe attributes to a model, such as wall thickness, for example, that don't change if it's scaled up or down - the wall always remains a certain thickness. This can be handy for designing something to be built from a particular material, as you can imagine.
If you're unsure about which program to get to deal with these formats, you might look at IronCAD; it supports all three.
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