multiple characters within single quotes

This is a discussion on multiple characters within single quotes within the C Programming forums, part of the General Programming Boards category; Can I place multiple characters within single quotes? For example, is the result of the following statement defined in C: ...

  1. #1
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    multiple characters within single quotes

    Can I place multiple characters within single quotes? For example, is the result of the following statement defined in C:

    Code:
    'abc';
    If this is defined, how does it work and which C standard supports it?

  2. #2
    Jack of many languages Dino's Avatar
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    No. Single quotes wrap single characters. That's the syntax.

    The only time > 1 character is allowed within single quotes is when the first character is an escape character.
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    Algorithm Dissector iMalc's Avatar
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    Quote Originally Posted by Todd Burch View Post
    No. Single quotes wrap single characters. That's the syntax.

    The only time > 1 character is allowed within single quotes is when the first character is an escape character.
    That's not entirely true. Multicharacter literals are part of the C standard. The following is valid C code:
    Code:
    int x = 'ABCD';
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    Quote Originally Posted by iMalc View Post
    The following is valid C code:
    Code:
    int x = 'ABCD';
    Yes, you can do this and for some reason it produces: x = 1094861636. There is not much reason to do so, x is not an address in memory nor is it multiplying the ASCII code for each character, thats what this does:
    Code:
    int x = 'A' * 'B'* 'C' * 'D'
    which also does not produce a warning. I can see more of a reason to multiply the ASCII code for each character as this can also be modified to use the other operations aswell, treating characters as numbers. It still is not explicit what the code will actually do reading it, characters are not generally thought of as their ASCII equivalent and other languages would probably crash when given the same code.
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    Quote Originally Posted by P4R4N01D View Post
    Yes, you can do this and for some reason it produces: x = 1094861636. There is not much reason to do so, x is not an address in memory nor is it multiplying the ASCII code for each character, thats what this does:
    Code:
    int x = 'A' * 'B'* 'C' * 'D'
    which also does not produce a warning. I can see more of a reason to multiply the ASCII code for each character as this can also be modified to use the other operations aswell, treating characters as numbers. It still is not explicit what the code will actually do reading it, characters are not generally thought of as their ASCII equivalent and other languages would probably crash when given the same code.
    This format is quite often used to make multibyte "magic" numbers, such as identifiers of file-formats (for example, BMP files contain 'BM' in the header).

    The value is actually ('A' << 24) + ('B' << 16) + ('C' << 8) + 'D', or ('D' << 24) + ('C' << 16) + ('B' << 8) + 'A' depending on the byte-order of the system.

    The real benefit of storing it as one int, rather than a character array, is that it can trivially be compared to another item of the same kind with one single instruction, rather than comparing a character array which requires (say) 4 operations, if you don't try to have fun with casting and pointers and such.

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