Some confusion of the character constant

Question

hi all,
   Consider the following problem:
first:

#include<stdio.h>
void main()
{
 char ch='\48';
  printf("%c\n",ch);
}
//Why the above code output is 8?

second:

#include<stdio.h>
void main()
{
 char *s="\ta\018bc";
 for(;*s!='\0';s++) printf("*");
}
//Why the above code output is 6 *?

thank very much.