Store multiple strings in a char array in C

If to place the missed semicolon at the end then this statement

const char temp[] = "GET / HTTP/1.0\r\n"
                    "Host:www.google.com\r\n"
                    "\r\n";

is equivalent to

const char temp[] = "GET / HTTP/1.0\r\nHost:www.google.com\r\n\r\n";

According to the C Standard in the section where translation phases are described there is written

6. Adjacent string literal tokens are concatenated

Sometines it is convinient to split a long string literal that does not fit a line into several shorter adjacent literals.

const char str[] = "stringstringstring";

const char str[] = "string" "string" "string";

const char str[] = "string"
              "string"
              "string";

#define NAME "string"
const char str[] = "string" NAME "string";

Will all have the same result. C concatenates adjacent strings.

It's a single string consisting of multiple concatenated string literals. The C language allows string literals that appear next to each other without any operator in between to be concatenated to form a single string. This is useful for string constants that span multiple lines of source, as you've seen. It's also useful when a preprocessor macro defines a string literal, you can write something like

#define BALANCE_FMT "%5.2f"
printf("Your balance is: " BALANCE_FMT "\n", balance);

C has string literal concatenation, meaning that adjacent string literals are concatenated at compile time; this allows long strings to be split over multiple lines, and also allows string literals resulting from C preprocessor defines and macros to be appended to strings at compile time.

For instance:

printf(__FILE__ ": %d: Hello "
       "world\n", __LINE__);

will expand to

printf("helloworld.c" ": %d: Hello "
       "world\n", 10);

which is syntactically equivalent to

printf("helloworld.c: %d: Hello world\n", 10);