Making a Calculator in Assembly (Little Man Computer)

You can multiply much more efficiently the way Egyptians used to do (http://www.jimloy.com/egypt/mult.htm[^]): let M x N, you will find the '1' bits in M and add N multiplied by the corresponding powers of 2, obtained by doubling.

Here is Python code that does it using only additions and comparisons:

M= 5
N= 9

# Accumulator
A= 0

while M > 0:
    # Power of 2
    W= 1
    NW= N

    # Find the leftmost bit in M
    while W + W < M:
        # Duplicate
        W= W + W
        NW= NW + NW

    # Accumulate
    A= A + NW

    # Erase the bit from M
    M= M - W

print A

Just compile this code to LittleMan assembly.

Note. This algorithm will perform O(m^2) additions, where m is the number of bits in M. [Maybe O(m) can be achieved, I am unsure.] In any case, this is far better than O(M) achieved by successive additions.

You can adapt these ideas to implement division, by subtracting N-times-a-power-of-2 from M.