explain me this c code plz
 

typedef u_long oid;
typedef u_char oid;
Can u explain me plz what the typedef means and what's the difference between u_long and u_char?
Thx a lot

The typedef statement just creates a new name for an existing type.
Those two statements will create a called oid which is the same as either a u_long or u_char. Presumably those two lines don't actually exist one after another in a source file?

As for the second question, u_long and u_char are both themselves created with typedefs from the standard C types unsigned long and unsigned char.