Question

Possible Duplicate:
Why #include <stdio.h> is *not* required to use printf()?

I am facing a problem in the below given code.

int main()
{
printf("\nHello Stack Overflow\n\n") ;
return 0 ;
}

In the above mentioned code i left including “#include “.
And if i compile and execute this piece of code, the output is printed as expected. But “#include ” being the most important thing in a C program, i have ignored it and still the compilation is done without any errors but with warning.

Why is this happening?

Answer 1

In C, functions that are not declared are implicitly considered to return an int and to take int arguments.

This is bad practice and will bite you. For example if you want to print data not the same size of an int, like double or float.