the multiplication table

Print the four-by-four multiplication table, rows of row * col padded into neat columns.

This is the nested-loop kata: an outer loop over rows, an inner loop over columns, a mulRd = Rn * Rm. Low bits only. in the middle, and a newline after each row. The cell format %4lld right-aligns every product into a four-character column so the table lines up.

One trap worth meeting on purpose: printf may scribble on the scratch registers, so both counters belong in the aliased callee-saved registers, not in x9caller-saved temporary (x9-x15): a called routine may overwrite it..

what is checked

• four rows of four aligned products
• the program exits cleanly
• the products come from mulRd = Rn * Rm. Low bits only. inside the loops