defining a 2D array with malloc and modifying it

Question

How do i define a 2D array using malloc ? (lets say 10X20).

second, can i increase number of rows or cols without creating a new increased array and copying all data

Answer 1

second, can i increase number of rows or cols without creating a new increased array and copying all data to it?

No, you can't change the size of an array. What you can do is use pointers and realloc to do so.