C Module 4 Quiz, Question #4

Question

I am so confused about question number 4. I initially felt like I understood pointers and the * and & operators, but I cannot seem to find anything on how to call this particular function pointer. Honestly, the whole idea of a function pointer seems completely convoluted to me; I just don't get it. If anybody has some insight as to the significance, syntax, or just the answer itself that would be really helpful. Thanks!

Answer 1

Perfect Answer :

#First blank is

Void

#Second blank is

&

#Third blank is

*

Answer 2

Fill in the blanks to triple the value of the num variable via the void pointer.
The correct ans :
float num = 3.14;

void
*ptr =
&
num;

*
((float*)ptr) *= 3;

Answer 3

Not a function pointer :) As Thirt13n pointed out we are just converting a float to a void* and back.

Truthfully C doesn't do a very good job of selling function pointers, the syntax is absolutely terrible.

Significance? In C probably not so much, but I see you did javascript aswell. This stuff is really common in js:

var f = function () { console.log("Hi!"); };
button.addEventListener("click", f);

In other words we can put functions in variables. Super useful, js devs do it *everywhere*.

Now in js everything is a `var` and it just sort of works somehow, but in C all variables need to have a type; and if you have a function in a variable, the variable's type needs to reflect the function's type somehow.

Thus we end up with gnarly stuff like `void (*foo)(int, int)`. Other languages have prettier syntax for function types but C is old what are you gonna do.

To translate the js example into nonsense C:

void f() { printf("Hi!"); }
void onEvent (char* what, void (*fp)()){ ... }

onEvent("click", &f);

Answer 4

float num=3.14;
void *ptr=#
*((float*)ptr)*=3;

Answer 5

ans =1

Answer 6

create a pointer to the variable called demo then output its value using the pointer

Answer 7

What is The largest of the arrays.if arrays form 35 12 3 8

Answer 8

Fill in the blanks to declare a string, then output its 5th character.

x[] = "Hello there
;
printf("
", x[
]);

Answer 9

Q.triple the value of " num " using void pointer

float num=3.14;
.......ptr=....num;
....((float*)ptr)*=3;

>>>as in question pointer " ptr " is void first blank's answer is " void " and then addressof " & "
>>>here num is casted to float , because when we dereference void pointer we must first type cast the pointer before dereferencing with " * " . ptr points to address of " num " if we dereference " ptr " then only we can make multiply to num , so third blank is for dereference " * " ;
here third " * " for multiplication !

HOPE THIS HELP !
(please correct me if I'm wrong)