Which matrices preserve range?

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Any matrix $M$ has a given range (column space). Let $B$ be a matrix such that for all $M$, $MB$ has the same column space as $M$. Clearly, the identity matrix $I$ satisfies this, as does any non-zero scalar multiple of $I$. Are there other matrices which satisfy this property for all $M$? Is there a name for matrices which satisfy this property? What about $BM$ instead of $MB$?

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They are called matrices of full row rank. That is, if $B$ is $m \times n$ (where the number $m$ of rows of $B$ is also the number of columns of $M$ in order for the multiplication $MB$ to be possible), $B$ must have rank $m$. Of course $n \ge m$ for this to be possible.

As for $BM$ (where this time $B$ must be a square matrix with the same number of columns as $M$ for the question to make sense), in order for $BM$ to always have the same column space as $M$, $B$ must be a nonzero scalar multiple of the identity matrix.