Prinf的格式化输出设置

Character	Type	Output format
c	int or wint_t	When used with printf functions, specifies a single-byte character; when used with wprintf functions, specifies a wide character.
C	int or wint_t	When used with printf functions, specifies a wide character; when used with wprintf functions, specifies a single-byte character.
d	int	Signed decimal integer.
i	int	Signed decimal integer.
o	int	Unsigned octal integer.
u	int	Unsigned decimal integer.
x	int	Unsigned hexadecimal integer, using "abcdef."
X	int	Unsigned hexadecimal integer, using "ABCDEF."
e	double	Signed value having the form [ – ]d.dddd e [sign]dd[d] where d is a single decimal digit, dddd is one or more decimal digits, dd[d] is two or three decimal digits depending on the output format and size of the exponent, and sign is + or –.
E	double	Identical to the e format except that E rather than e introduces the exponent.
f	double	Signed value having the form [ – ]dddd.dddd, where dddd is one or more decimal digits. The number of digits before the decimal point depends on the magnitude of the number, and the number of digits after the decimal point depends on the requested precision.
g	double	Signed value printed in f or e format, whichever is more compact for the given value and precision. The e format is used only when the exponent of the value is less than –4 or greater than or equal to the precision argument. Trailing zeros are truncated, and the decimal point appears only if one or more digits follow it.
G	double	Identical to the g format, except that E, rather than e, introduces the exponent (where appropriate).
a	double	Signed hexadecimal double precision floating point value having the form [−]0xh.hhhh p±dd, where h.hhhh are the hex digits (using lower case letters) of the mantissa, and dd are one or more digits for the exponent. The precision specifies the number of digits after the point.
A	double	Signed hexadecimal double precision floating point value having the form [−]0Xh.hhhh P±dd, where h.hhhh are the hex digits (using capital letters) of the mantissa, and dd are one or more digits for the exponent. The precision specifies the number of digits after the point.
n	Pointer to integer	Number of characters successfully written so far to the stream or buffer; this value is stored in the integer whose address is given as the argument. See Security Note below.
p	Pointer to void	Prints the argument as an address in hexadecimal digits.
s	String	When used with printf functions, specifies a single-byte–character string; when used with wprintf functions, specifies a wide-character string. Characters are printed up to the first null character or until the precision value is reached.
S	String	When used with printf functions, specifies a wide-character string; when used with wprintf functions, specifies a single-byte–character string. Characters are printed up to the first null character or until the precision value is reached.

不要觉得简单，当输出unsigned int时，很少有人能很快做对，该用的是%u,而不是%d.

Wentao Sun.