CODEWITHSUNDEEP
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Krish
Krish

Reputation: 575

Why do '?' and '\?' give the same output in C?

In C, why do these two pieces of code give the same output?

#include<stdio.h>

int main(void)
{
    const char c='\?';
    printf("%c",c);
}

and

#include<stdio.h>

int main(void)
{
    const char c='?';
    printf("%c",c);
}

I understand that a backslash is used to make quotes (" or ') and a backslash obvious to the compiler when we use printf(), but why does this work for the '?'?

Upvotes: 48

Views: 4502

Answers (5)

Ajay Brahmakshatriya
Ajay Brahmakshatriya

Reputation: 9203

Quoting C11, chapter §6.4.4.4p4

The double-quote " and question-mark ? are representable either by themselves or by the escape sequences \" and \?, respectively, but ... .

Emphasis mine

So the escape sequence \? is treated the same as ?.

Upvotes: 29

keivan shirkoubian
keivan shirkoubian

Reputation: 75

when you're defining a char or string the compiler parses backslash in that char or string as an escape sequence.

Upvotes: 0

Shashank Singh Bisht
Shashank Singh Bisht

Reputation: 81

**

the simple answer of your question is 
\? means ?. instead of using \? you can using ? .
\? is escape representation and ? is character representation means both are same.

i have linked a image so that you understand it more easily..

**

"click here to see the image " --> in this image you need to find \? in Escape character

Upvotes: -1

Bathsheba
Bathsheba

Reputation: 234785

\? is an escape sequence exactly equivalent to ?, and is used to escape trigraphs:

#include <stdio.h>
int main(void) {
    printf("%s %s", "??=", "?\?="); // output is # ??=
}

Upvotes: 86

Some programmer dude
Some programmer dude

Reputation: 409364

Because '\?' is a valid escape code, and is equal to a question-mark.

Upvotes: 20

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