C function syntax, parameter types declared after parameter list -

i'm relatively new c. i've come across form of function syntax i've never seen before, parameter types defined after parameter list. can explain me how different typical c function syntax?

example:

int main (argc, argv) int argc; char *argv[]; { return(0); } 

that's old-style syntax parameter lists, still supported. in k&r c leave off type declarations , default int. i.e.

main(argc, argv) char *argv[]; {     return 0; } 

would same function.