difference between calling a function when it is pointed by a pointer and not pointed by a pointer

Question

may I know what are the differences in the way the function foo is being called here:

Answer 1

In (1), main calls go and passes the address of foo in the call. In (2), main calls go and does not pass any argument. ( foo designates the function foo . However, when a function designator is used in an expression other than as the operand of sizeof or of unary & , it is automatically converted to a pointer to the function. So go(foo) is equivalent to go(&foo) .)

In (1), go takes a parameter that is a pointer to a function with unspecified parameters and return type void . In (2), go does not take any parameters.

In (1), go calls the function whose address it was passed, by using its parameter proc . In (2), go calls foo . (As above, although foo is used in foo(); , it is automatically converted to an address, as if (&foo)(); had been written. All function calls actually use the address of the function, even if function designator is used.)