Suppose you have an NxN matrix and you have to check whether it's a upper diagonal matrix or not. Is there any generic method to solve this problem?

I am elaborating my question: Some thing is like this: Suppose you have NXN matrix having the value of N=4 then matrix will look like this:

|5 6 9 2|
|1 8 4 9|
|5 8 1 6|
|7 6 3 2|

Its a 4X4 square matrix and again if it's upper triangle matrix it will look something like this:

|5 6 9 2|
|1 8 4 0|
|5 8 0 0|
|7 0 0 0|

I need to generate a generic program in any language to check wether a square matrix is upper trailgle or not.