const char* initialization

Question

This is one usage I found in a open source software.And I don't understant how it works. when I ouput it to the stdout,it was "version 0.8.0".

const char version[] = " version " "0" "." "8" "." "0";

Answer 1

It's called string concatenation -- when you put two (or more) quoted strings next to each other in the source code with nothing between them, the compiler puts them together into a single string. This is most often used for long strings -- anything more than one line long:

char whatever[] = "this is the first line of the string\n"
    "this is the second line of the string\n"
    "This is the third line of the string";

Before string concatenation was invented, you had to do that with a rather clumsy line continuation, putting a backslash at the end of each line (and making sure it was the end, because most compilers wouldn't treat it as line continuation if there was any whitespace after the backslash). There was also ugliness with it throwing off indentation, because any whitespace at the beginning of subsequent lines might be included in the string.

This can cause a minor problem if you intended to put a comma between the strings, such as when initializing an array of pointers to char. If you miss a comma, the compiler won't warn you about it -- you'll just get one string that includes what was intended to be two separate ones.