Expert C Programming reading

1. Both operands are pointers to qualified or unqualified versions of compatible types, and the type pointed to by the left has all the qualifiers of the type pointed to by the right. 

char * cp;
const char *ccp;
ccp = cp;

cp = ccp; /* results in a compilation warning */

2.The one "l" NUL ends an ASCII string, The two "l" NULL points to no thing.