Who was your interviewer? They both mean the same thing, there's no difference in that case. [font=courier new,courier,monospace]const[/font] binds to the thing on it's left, but if there's nothing on it's left then it will happily bind to the thing on it's right.
So in "[font=courier new,courier,monospace]char const x[/font]" const binds to the thing on it's left, producing a "[font=courier new,courier,monospace]char+const[/font]" type. And in "[font=courier new,courier,monospace]const char x[/font]", there's nothing on the left of const, so it binds to the thing on it's right, also producing a "[font=courier new,courier,monospace]char+const[/font]" type.

If the type is a pointer, then the placement of const does have a significant impact:
A) [font=courier new,courier,monospace]const char* x;//[/font] a mutable pointer, pointing to a read-only char
B) [font=courier new,courier,monospace]char* const x;//[/font] a read-only pointer, pointing to to a mutable char
C) [font=courier new,courier,monospace]const char* const x;//[/font] a read-only pointer, pointing to a read-only char
D) [font=courier new,courier,monospace]char const* x; //[/font] same as A
E) [font=courier new,courier,monospace]char const* const x; //[/font] same as C

I'd agree with Marvel: if I got this question, I'd immediately ask if they meant it to include a pointer or not, as that's where it begins to really matter (as per Hodgman's clear explanation above)

Though that's a specific C "gotcha", unless the job is rooted in C (or C++) development it wasn't a very good interview question. You've either had to fudge around with pointers in C or you haven't, but that isn't necessarily going to indicate you're a better programmer. (What should have been more important is how quickly you would pick this up if you hadn't already worked with it before)