C - Difference between quotation and apostrophe ( " vs ' )

Question

In C it has come to attention that there is a difference between these 2 specified syntax. Observe

 char test[5] = {"c", "o", "o", "l", "\0"}; // with quotation

bring about error:

error: (near initialization for 'test')
error: excess elements in char array initializer
error: (near initialization for 'test')
error: excess elements in char array initializer
error: (near initialization for 'test')
error: excess elements in char array initializer
error: (near initialization for 'test')

Where as

char test[5] = {'c', 'o', 'o', 'l', '\0'}; // with apostrophe

Compiles finely. What is the cause of this?

`'x'` is a character literal. `"x"` is a string literal containing one character. — Ry-, Sep 23 '15 at 04:57

score 2 · Answer 1 · answered Sep 23 '15 at 04:57

2

In C, when you are using single quotes then it means a character and a double quotes means string literal. And since you declared your array as char hence it cannot store string in that.

answered Sep 23 '15 at 04:57

Rahul Tripathi

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Raman · Answer 2 · 2015-09-23T05:04:58.240

2

"x" is not a character, Its a string literal. It is same as an array of two characters 'x' and '\0'.

I think of it like this:

       _ _ _ _ _
"x" => |'x'|'\0'| 
       - - - - -

edited Sep 23 '15 at 05:04

answered Sep 23 '15 at 04:59

Raman

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paulsm4 · Accepted Answer · 2015-09-23T07:50:27.857

2

The elements in this array are characters (1 byte each):

char test[5] = {'c', 'o', 'o', 'l', '\0'};

This is a null-terminated C string. It's represented exactly the same way in memory. It consists of exactly 5 bytes: the letters "cool", and the terminating null character:

char test2[5] = {"cool"};

And this consists of two bytes:

char test3[] = "c";

Your original example is an array of 2-byte strings. Unlike the previous examples, it's actually a 2-level array. You must declare it as such:

char *test[] = {"c", "o", "o", "l", "\0"};

edited Sep 23 '15 at 07:50

answered Sep 23 '15 at 05:00

paulsm4

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@Blastfurnace - that was a typo, Thank you for pointing it out :) – paulsm4 Sep 23 '15 at 07:51

score 2 · Answer 4 · answered Sep 23 '15 at 05:04

char test[5] = {'c', 'o', 'o', 'l', '\0'}; // with apostrophe

is the correct syntax because, as you have declared, test is an array of characters which can store 5 characters.

char* test[5] = {"c", "o", "o", "l", "\0"}; // with quotation

This is acceptable, since you are declaring that test is an array of pointers to character strings.

Run the following code in ideone.com and see.

#include <stdio.h>

int main(void) {
// your code goes here

char* teststring[5] = {"c", "o", "o", "l", "\0"}; // with quotation

char testchar[5] = {'c', 'o', 'o', 'l', '\0'};
printf("%s\n", teststring[2]);

printf("%c\n", testchar[2]);

return 0;
}

score 1 · Answer 5 · answered Sep 23 '15 at 05:05

In C,

Two single quotes, ', are used to represent a character constant.
Two double quotes, ", are used to represent a string literal.

A character constant can represent one character only. 'ab' is not a valid character constant.

A string literal can contain multiple characters.

C - Difference between quotation and apostrophe ( " vs ' )

5 Answers5