Let $A=[a_{ij}]$ be a matrix with $\infty$ rows and $\infty$ columns with entries in a vector space, also $A_n=[b_{ij}]$ a matrix with $\infty$ rows and $\infty$ columns when $b_{ij}=a_{ij}$ for $i,j\leq n$ and $b_{ij}=0$ for $i,j>n$.
Is $A=\sup A_n$ Correct or not? why?
Can introduced me a reference about these matrices?