C Can anyone explain this syntax?

Question

Why is the variable "char *s" declared in between the function name and curly braces? What is the significance of it?

 main(m1,s) char *s; {
     /*
       some code here
     */
}

Answer 1

This is old K&R C syntax (pre-dates ANSI/ISO C). Nowadays, you should not use it anymore (as you have already noticed its major disadvantage: the compiler won't check the types of arguments for you).

 main(m1,s) char *s; {
     /*
       some code here
     */
}

in this code compiler did not check data type of m1 and s.