Sudoku-Solver

C code to solve SUDOKU

I am uploading my code for the first time, so don't exactly understand what to write here !
Well,
this project contains the C code which solves the very old puzzle SUDOKU programmatically. Approximately taking around 25ms to solve each question.

The code is well tested in gcc compiler. (anyone is free to comment on any line of the code, if you feel anything could have been done). Code uses backtracking approach. (important : code outputs all possible outcomes for a particular question).
For testing purpose I am uaing "test.txt" as the input file to get the input to the program. I am using 0 to indicate blank to make my life easy.