Prototype Declaration

1...The given code has no prototype declaration for the function 'printer', but it still compiles. Is the prototype of a function optional?

2...The result on running is a huge real number with many zeros?

3...The code doesn't build if i change the parameter of 'printer' to 'float num'?
(though the current code compiles fine)

Code:

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#include <stdio.h>

int main() {
  // int printer(double);    -----------> i removed the prototype declaration
    printer(10);
    return 0;
}
int printer(double num){
    printf("Hello!  %f  ",num);
    return 0;
}

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Quote:

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Originally Posted by rrahulvverma

1...The given code has no prototype declaration for the function 'printer', but it still compiles. Is the prototype of a function optional?

2...The result on running is a huge real number with many zeros?

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At the call site, the return type and parameter types will be assumed to default to int, which in this case (and more generally) is not what you want.

Quote:

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Originally Posted by rrahulvverma

3...The code doesn't build if i change the parameter of 'printer' to 'float num'?
(though the current code compiles fine)

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I cannot say that I am very clear on why this is so, but rather than search and tell you the exact reason, the simple solution is: don't do it, i.e., ensure that a declaration of the function is available at the point the function is called.

Function prototypes are supposed to be before the functions that use them; Never inside any function like main.

Tim S.

Quote:

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Originally Posted by stahta01

Function prototypes are supposed to be before the functions that use them; Never inside any function like main.

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Actually, unless the function declaration is also a function definition, a function declaration is permitted within the body of a function.

Are 1,2,3 your quiz questions which you're expected to answer "yes" or "no" to?

Quote:

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Originally Posted by Salem

Are 1,2,3 your quiz questions which you're expected to answer "yes" or "no" to?

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No! :D

(and actually, except for my first 'quiz' question, a "yes/no" answer for the other ones might sound a little stupid, i guess)

Anyways, your sense of humor is appreciated!

Thanks 'laserlight'! :)