What does casting do?

Question

Should be 7 in ASCII the output?

#include <bits/stdc++.h>
using namespace std; 
int main() {
    char a = '7'; 
    int b = 7;
    cout << (char)b;
}

No, numbers aren't casted to ASCII, and ASCII chars aren't casted from digits to the corresponding integer values. — πάντα ῥεῖ, Feb 07 '21 at 12:17
You program should 'ring the bell' (or make some other alert sound). The ASCII character with a value of 7 is `bel`. — Adrian Mole, Feb 07 '21 at 12:18
There is no known encoding where `'7' == 7`. It's definitely not the case with ASCII where `'7'` is `55`. — Some programmer dude, Feb 07 '21 at 12:18
And please don't include ``, it's [a really bad habit](https://stackoverflow.com/questions/31816095/why-should-i-not-include-bits-stdc-h). As is [`using namespace std;`](https://stackoverflow.com/questions/1452721/why-is-using-namespace-std-considered-bad-practice) — Some programmer dude, Feb 07 '21 at 12:19
@Fabbiucciello because the namespace is there for a reason. Moving the entire namespace to the global namespace removes the protection. — Clifford, Feb 07 '21 at 12:40

Clifford · Answer 1 · 2021-02-07T12:28:39.027

2

Clearly not, because the ASCII code for '7' is 0x37 (55). ASCII 7 is the BEL control character. If supported by the particular environment you run it on, it will issue some alert sound or beep.

In this case the cast causes std::ostream::operator<<(char) rather then std::ostream::operator<<(int) to be called, emitting the character BEL ('\a' or 7) to be emitted rather then presenting a decimal string representing the integer value 7.

edited Feb 07 '21 at 12:28

answered Feb 07 '21 at 12:22

Clifford

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std::ostream::operator<<(int) what does it mean ? – Fabbiucciello Feb 07 '21 at 12:25
@Fabbiucciello This is the overloaded stream operator for formatted output of `int`: [std::ostream& std::ostream::operator<<(int)](https://en.cppreference.com/w/cpp/io/basic_ostream/operator_ltlt). It makes that `std::cout << 123;` does what it does. – Scheff's Cat Feb 07 '21 at 12:27
@Fabbiucciello Maybe you should post that as a separate questuion. `<<` is an overloaded operator of the `ostream` class; it is not _built-in_ to the language. When you use `<<` and the left-hand operand is an `std::ostream` object (as `cout` is), then an `ostream` member function called `operator<<` is called of which there are several versions, and the one called depends on the _type_ of the right-hand operand. http://www.cplusplus.com/reference/ostream/ostream/operator%3C%3C/ – Clifford Feb 07 '21 at 12:33

What does casting do?

1 Answers1