  For each function on bit strings, its restriction to bit strings of any given
length can be computed by a finite instruction sequence that contains only
instructions to set and get the content of Boolean registers, forward jump
instructions, and a termination instruction. We describe instruction sequences
of this kind that compute the function on bit strings that models
multiplication on natural numbers less than $2^N$ with respect to their binary
representation by bit strings of length $N$, for a fixed but arbitrary $N > 0$,
according to the long multiplication algorithm and the Karatsuba multiplication
algorithm. We find among other things that the instruction sequence expressing
the former algorithm is longer than the one expressing the latter algorithm
only if the length of the bit strings involved is greater than $2^8$. We also
go into the use of an instruction sequence with backward jump instructions for
expressing the long multiplication algorithm. This leads to an instruction
sequence that it is shorter than the other two if the length of the bit strings
involved is greater than $2$.
