In C, a string literal is a string of characters enclosed in double quotes, such as "a computer".
String literals are stored in C as an array of chars, terminted by a null byte. A null byte is a char having a value of exactly zero, noted as '\0'. Do not confuse the null byte, '\0', with the character '0', the integer 0, the double 0.0, or the pointer NULL.
String literals may contain as few as one or even zero characters. Do not confuse a single-character string literal, e.g. "A" with a character constant, 'A'. The former is actually two characters, because of the terminating null byte stored at the end.
An empty string, "", consists of only the null byte, and is considered to have a string length of zero, because the terminating null byte does not count when determining string lengths.
String literals may contain any valid characters, including escape sequences such as \n, \t, etc. Octal and hexadecimal escape sequences are technically legal in string literals, but not as commonly used as they are in character constants, and have some potential problems of running on into following text.
String literals can be concatenated at compile time: "hello, " "world" is equivalent to "hello, world". This is useful for splitting up long strings across several source lines.