整数相加
$$
\begin{array}{l}
\mathbf {procedure} ; \mathcal {add} (a, b:integer)\
{a和b的二进制展开分别是(a_{n-1}a_{n-2}\dots a_1a_0)2和(b{n-1}b_{n-2}\dots b_1b_0)2} \
c:= 0 \
\mathbf {for}; j:=0 ;\mathbf {to}; n-1 \
\mathbf {begin} \
\qquad d:=\lfloor (a_j+b_j+c)/2\rfloor \
\qquad s_j:=a_j+b_j+c-2d \
\qquad c:=d \
\mathbf {end} \
s_n := c \
{和数的二进制展开是(s_ns{n-1}\dots s_0)_2}
\end{array}
$$
整数相乘
$$
\begin{array}{l}
\mathbf {procedure} ;\mathcal {multiply} (a, b:integer)\
{a和b的二进制展开分别是(a_{n-1}a_{n-2}\dots a_1a_0)2和(b{n-1}b_{n-2}\dots b_1b_0)2} \
\mathbf {for}; j:=0 ;\mathbf {to}; n-1 \
\mathbf {begin} \
\qquad \mathbf {if}; b_j=1;\mathbf {then}; c_j:=a;shifted; j places \
\qquad \mathbf{else}; c_j:=0\
\mathbf {end} \
{c_0,c_1,\dots,c{n-1}是部分乘积} \
p:=0\
\mathbf {for}; j:=0;\mathbf {to}; n-1 \
\qquad p:=p+c_j \
{p是ab的值}
\end{array}
$$