printf("\%")

[bawasngtatlo]

Hello guys, new here, I'm just wonderin' why does it prints nothing? any idea behind it?

I'm not trying to print "%", cause I know how to, what I am curios about is what is happening underneath it?

EDIT:

To summarize, since "printf never sees the \ character" and at compile time printf("\%") backslash will just be ignored since escaping modulus with backslash is not possible, and maybe that's why they use another character to escape it. Thanks Disch.

[Disch]

\ is an escape character, meaning the next character(s) in the string is a special code. It is used to represent characters which are not easy to type.

Examples:

\n is a newline
\r is a carriage return
\t is a tab
\1 is the literal value of 1
\" is a quotation mark (so you can have a quotation mark in the middle of a string literal without ending the string
etc
etc


% is not a valid character to escape. So \% is an invalid escape sequence. Which is why it prints nothing for you. Your compiler should at least be giving you a warning of this.

[bawasngtatlo]

well compiler does not, thanks for the fast response, but in std::cout it escape the character modulus, so i guess printf just ignore the backslash before the "%", because i tried printf("\%d", 0), it just ignores the backslash and giving me an output of 0.

[bawasngtatlo]

also anyone knows why printf use another "%" to escape the character "%"? and not "\"?

[Disch]

That makes sense.... it's a bad escape sequence so it just throws out the escape character (\) and leaves the rest of the string (%d) in tact.

[Disch]

also anyone knows why printf use another "%" to escape the character "%"? and not "\"?

Because printf never sees the \ character. That's escaped by the compiler at compile time before the string gets passed to printf at runtime.

EDIT:

and it would conflict with printf format rules anyway:

printf("\02d", 5);  // does this print "05" as per normal printf operation?
    // or does it print "?5" where '?' is the ASCII code with value=2 as the escape sequence would? 

[bawasngtatlo]

I don't understand what your "EDIT" portion is for. Now I know it happens at compile time. So to summarize, since "printf never sees the \ character" and at compile time printf("\%") backslash will just be ignored since escaping modulus with backslash is not possible, and maybe that's why they use another character to escape it.