[急求] 高精度乘法
请您 附高精度乘法的程序及此每一步的具体说明；
或说明以下例程的思想及分析每一步的具体实现方式（解读例程。）谢谢！
ps:请于11.18日9:30前回复本贴！不胜感激！
.高精度乘高精度
程序如下:
program HighPrecision4_Multiply2;
const
fn_inp='hp4.inp';
fn_out='hp4.out';
maxlen=100; { max length of the number }
type
hp=record
len:integer; { length of the number }
s:array[1..maxlen] of integer
{ s[1] is the lowest position
s[len] is the highest position }
end;
var
x:array[1..2] of hp;
y:hp; { x:input ; y:output }
procedure PrintHP(const p:hp);
var i:integer;
begin
for i:=p.len downto 1 do write(p.s);
end;
procedure init;
var
st:string;
j,i:integer;
begin
assign(input,fn_inp);
reset(input);
for j:=1 to 2 do
begin
readln(st);
x[j].len:=length(st);
for i:=1 to x[j].len do { change string to HP }
x[j].s:=ord(st[x[j].len+1-i])-ord('0');
end;
close(input);
end;
procedure Multiply(a,b:hp;var c:hp); { c:=a+b }
var i,j,len:integer;
begin
fillchar(c,sizeof(c),0);
for i:=1 to a.len do
for j:=1 to b.len do
begin
inc(c.s[i+j-1],a.s*b.s[j]);
inc(c.s[i+j],c.s[i+j-1] div 10);
c.s[i+j-1]:=c.s[i+j-1] mod 10;
end;
len:=a.len+b.len+1;
{
the product of a number with i digits and a number with j digits
can only have at most i+j+1 digits
}
while(len>1)and(c.s[len]=0) do dec(len);
c.len:=len;
end;
procedure main;
begin
Multiply(x[1],x[2],y);
end;
procedure out;
begin
assign(output,fn_out);
rewrite(output);
PrintHP(y);
writeln;
close(output);
end;
begin
init;
main;
out;
end.
