WHAT DOES THIS CODE DO? Can side notes be added to each line to label what each section does and how can this be more efficient?

char* a a, char* b) int la strlen(a), int lb strlen(b); int lr la lb la lb; int carry 0; char *res (char*)calloc(lr 2, sizeof(char); res Ir 11 10: la--; lb while (la 0 ll lb 00 int ba la int bb 1b 0 bLlb--] -'0' 0 int br ba bb A carry; carry B (ba & bb) ca & (ba bb); if (carry) return res 1; res '1'; return res