大数乘法c++

#include<stdio.h>
#include<string.h>

#define max 100
#define maxlen(a,b) (a>b)?a:b
#define minlen(a,b) (a>b)?b:a
char a[max];
char b[max];
int  c[max][2*max+1];
int sum[2*max+1];

void caculate(int j,int a1[],int b,int n1)
{

int carry=0,i;
int n=n1;

for(i=0;i<n;i++)
{

c[j][j+i]=(b*a1[i]+carry)%10;
carry=(b*a1[i]+carry)/10;
}
if(carry>0)
c[j][n+j]=carry;
/*for(i=0;i<n+j;i++)
   printf("%d ",c[j][i]);
printf("\n");
*/