typedef char* ptr; ptr a, b, c; the statement effectively becomes char *a, *b, *c; This declares a, b, c as char*. In contrast, #define works like this: #define PTR char* PTR x, y, z; the statement effectively becomes char *x, y, z;**Difference** 1) typedef is limited to giving symbolic names to types only, whereas #define can be used to define an alias for values as well, e.g., you can define 1 as ONE, 3.14 as PI, etc. 2) typedef interpretation is performed by the compiler where #define statements are performed by preprocessor. 3) #define should not be terminated with a semicolon, but typedef should be terminated with semicolon. 4) #define will just copy-paste the definition values at the point of use, while typedef is the actual definition of a new type. 5) typedef follows the scope rule which means if a new type is defined in a scope (inside a function), then the new type name will only be visible till the scope is there. In case of #define, when preprocessor encounters #define, it replaces all the occurrences, after that (No scope rule is followed).