Data structure used for implementing spreadsheets

Question

What is the data structure used by spreadsheets program like ms-excel?

Answer 1

I got this question in an interview today.

The answer they were looking for (because I asked the interviewer at the end) was to implement a class structure that used multiple objects; formulas, references, and numerics.

Not much more detail to offer but suffice it to say that programs like google docs are much more interesting (to code) than they seem.

Answer 2

I expect it to use many.

For example, an AST to recalculate formulas (see this question).

Answer 3

While it is not exactly Excel, Open Office's Spreadsheet program is open source. It's a fairly large code base but nevertheless giving it a peek might give you a better understanding of how such an application is implemented:

http://contributing.openoffice.org/programming.html

Answer 4

Possibly a multi-dimensional array.

Answer 5

Maybe, probably, a sparse matrix:

http://en.wikipedia.org/wiki/Sparse_matrix