jbk1

jbk1

a,b,c,d := c,d,a-c*q,b-d*q

declare 4 temporary variables ta, tb, tc, td

then do

ta = a;
tb = b;
tc = c;
td = d;

then do

a = tc;
b = td;
c = ta - tc*q;
d = tb - td*q;