Out of all the combinations you tried, %ld
and %lu
are the only ones which are valid printf format specifiers at all. %lu
(long unsigned decimal), %lx
or %lX
(long hex with lowercase or uppercase letters), and %lo
(long octal) are the only valid format specifiers for a variable of type unsigned long (of course you can add field width, precision, etc modifiers between the %
and the l
).