Here is the standard prototype of printf function in C.
int printf(const char *format, ...);
The format string is composed of zero or more directives: ordinary characters (not %), which are copied unchanged to the output stream; and conversion specifications, each of argument (and it is an error if insufficiently many arguments are given).
The character % is followed by one of the following characters.
The flag character
The field width
The length modifier
The conversion specifier: