If the return value type of the custom function is not written, does it return int by default? Does fun(int x) return int? Do I have to write the parameter type int?

(1) If the return value type is not written, the int type -correct will be returned by default.

Fun(int x) returns an int-correct.

(2) 2) Do you have to write the fun (int x) parameter type int?

Answer: It is related to the compiler. MS VC++ 6.0 can be omitted, and the default is int type.

For example:

# include & ltstdio.h & gt

fun(x){ return x * x； }

main(){

int y = 3；

printf("%d "，fun(y))；

}

Output 9

Old-fashioned programs, parameter types are declared after parentheses, and types are not written in parentheses:

# include & ltstdio.h & gt

Floating fun (x)

Floating x;

{ return x * x}

main(){

float y = 3；

printf("%f "，fun(y))；

}

(3) Function prototype declaration can only write types, not parameters, such as:

float fun(int，int)；

(4) It is suggested to write the return type, parameter type and parameter name correctly.