//Program to add 1 in very big number

#include "stdio.h"
#include "string.h"

void add_one(char *num)
{
    int l = strlen(num);  
   char *res = (char *)malloc (l+1);

   memset(res,'0',l+1);
   memcpy(res+1,num,l);
   res[l+1] = '\0';
   while(*(res+ l) == '9')
   {
    *(res+ l) = '0';
     l--;
   }
    *(res+ l) = *(res+ l) + '1' - '0';
    printf( "result--> %s" , res + (*res=='0')); 
}
int main()
{
  add_one("123");
return 0;
}

result--> 124