Basic question about matrix algebra- notation

Question

The representation $X=(I_p,0_{n-p\times p})$is confusing me. I get that $I_p$ is an identity matrix with $p$ rows and columns and the rest of the representation is confusing me. Can someone clarify this -simple notation-especially the dimension of $X$?

Answer 1

It's just a typo and should read $(I_p, 0_{p\times(n-p)})$.