Here is a solution just using search, add and move. The search does not require multiplication, since it is an array of pointers to another array, so you need to find the correct array. Then, using the second value, you can repeat the arithmetic of the pointer and get the search result.
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char **argv)
{
/* Note:As this is an array of pointers to an array of values, addition is
only required for the lookup.
i.e.
First part: lookup + a value -> A pointer to an array
Second part - Add a value to the pointer to above pointer to get the value
*/
unsigned char lookup[16][16] = {
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 },
{ 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30 },
{ 0, 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, 42, 45 },
{ 0, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52, 56, 60 },
{ 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 },
{ 0, 6, 12, 18, 24, 30, 36, 42, 48, 54, 60, 66, 72, 78, 84, 90 },
{ 0, 7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84, 91, 98, 105 },
{ 0, 8, 16, 24, 32, 40, 48, 56, 64, 72, 80, 88, 96, 104, 112, 120 },
{ 0, 9, 18, 27, 36, 45, 54, 63, 72, 81, 90, 99, 108, 117, 126, 135 },
{ 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150 },
{ 0, 11, 22, 33, 44, 55, 66, 77, 88, 99, 110, 121, 132, 143, 154, 165 },
{ 0, 12, 24, 36, 48, 60, 72, 84, 96, 108, 120, 132, 144, 156, 168, 180 },
{ 0, 13, 26, 39, 52, 65, 78, 91, 104, 117, 130, 143, 156, 169, 182, 195 },
{ 0, 14, 28, 42, 56, 70, 84, 98, 112, 126, 140, 154, 168, 182, 196, 210 },
{ 0, 15, 30, 45, 60, 75, 90, 105, 120, 135, 150, 165, 180, 195, 210, 225 }
};
unsigned short answer, mult;
unsigned char x, y, a, b;
x = (unsigned char)atoi(argv[1]);
y = (unsigned char)atoi(argv[2]);
printf("Multiple %d by %d\n", x, y);
answer = 0;
/* First nibble of x, First nibble of y */
a = x & 0xf;
b = y & 0xf;
mult = lookup[a][b];
answer += mult;
printf("Looking up %d, %d get %d - Answer so far %d\n", a, b, mult, answer);
/* First nibble of x, Second nibble of y */
a = x & 0xf;
b = (y & 0xf0) >> 4;
mult = lookup[a][b];
answer += mult << 4;
printf("Looking up %d, %d get %d - Answer so far %d\n", a, b, mult, answer);
/* Second nibble of x, First nibble of y */
a = (x & 0xf0) >> 4;
b = y & 0xf;
mult = lookup[a][b];
answer += mult << 4;
printf("Looking up %d, %d get %d - Answer so far %d\n", a, b, mult, answer);
/* Second nibble of x, Second nibble of y */
a = (x & 0xf0) >> 4;
b = (y & 0xf0) >> 4;
mult = lookup[a][b];
answer += mult << 8;
printf("Looking up %d, %d get %d - Answer so far %d\n", a, b, mult, answer);
return 0;
}