Most of what a devops person does is in fact development but it is of the non value adding variety. Basically a devops person spends the vast majority of their time configuring common off the shelf software, scripting this or that, etc.
A singular matrix is a matrix which has no inverse because its determinant is zero. If you recall, the inverse of a matrix is. 1/ ad-bc multiplied by: [ d -b ] [-c a ] If ad-bc = 0, then the inverse matrix would not exist because 1/0 is undefined, and hence it would be a singular matrix. E.g.
A matrix is a rectangular array of numbers arranged in rows and columns. The array of numbers below is an example of a matrix. The number of rows and columns that a matrix has is called its dimension or its order. By convention, rows are listed first; and columns, second.