A format specifier follows this prototype:
%[flags][width][.precision][length]specifier
specifier 
Output 
Example 
d or i 
Signed decimal integer 
392 
u 
Unsigned decimal integer 
7235 
o 
Unsigned octal 
610 
x 
Unsigned hexadecimal integer 
7fa 
X 
Unsigned hexadecimal integer (uppercase) 
7FA 
f 
Decimal floating point, lowercase 
392.65 
F 
Decimal floating point, uppercase 
392.65 
e 
Scientific notation (mantissa/exponent), lowercase 
3.9265e+2 
E 
Scientific notation (mantissa/exponent), uppercase 
3.9265E+2 
g 
Use the shortest representation: %e or %f 
392.65 
G 
Use the shortest representation: %E or %F 
392.65 
a 
Hexadecimal floating point, lowercase 
0xc.90fep2 
A 
Hexadecimal floating point, uppercase 
0XC.90FEP2 
c 
Character 
a 
s 
String of characters 
sample 
p 
Pointer address 
b8000000 
n 
Nothing printed. The corresponding argument must be a pointer to a signed int. The number of characters written so far is stored in the pointed location. 

% 
A % followed by another % character will write a single % to the stream. 
% 
flags 
description 
 
Leftjustify within the given field width; Right justification is the default (see width subspecifier). 
+ 
Forces to preceed the result with a plus or minus sign (+ or ) even for positive numbers. By default, only negative numbers are preceded with a  sign. 
(space) 
If no sign is going to be written, a blank space is inserted before the value. 
# 
Used with o, x or X specifiers the value is preceeded with 0, 0x or 0X respectively for values different than zero. Used with a, A, e, E, f, F, g or G it forces the written output to contain a decimal point even if no more digits follow. By default, if no digits follow, no decimal point is written. 
0 
Leftpads the number with zeroes (0) instead of spaces when padding is specified (see width subspecifier). 
width 
description 
(number) 
Minimum number of characters to be printed. If the value to be printed is shorter than this number, the result is padded with blank spaces. The value is not truncated even if the result is larger. 
* 
The width is not specified in the format string, but as an additional integer value argument preceding the argument that has to be formatted. 
.precision 
description 
.number 
For integer specifiers (d, i, o, u, x, X): precision specifies the minimum number of digits to be written. If the value to be written is shorter than this number, the result is padded with leading zeros. The value is not truncated even if the result is longer. A precision of 0 means that no character is written for the value 0. For a, A, e, E, f and F specifiers: this is the number of digits to be printed after the decimal point (by default, this is 6). For g and G specifiers: This is the maximum number of significant digits to be printed. For s: this is the maximum number of characters to be printed. By default all characters are printed until the ending null character is encountered. If the period is specified without an explicit value for precision, 0 is assumed.

.* 
The precision is not specified in the format string, but as an additional integer value argument preceding the argument that has to be formatted. 
The length subspecifier modifies the length of the data type. This is a chart showing the types used to interpret the corresponding arguments with and without length specifier (if a different type is used, the proper type promotion or conversion is performed, if allowed):

specifiers 
length 
d i 
u o x X 
f F e E g G a A 
c 
s 
p 
n 
(none) 
int 
unsigned int 
double 
int 
char* 
void* 
int* 
hh 
signed char 
unsigned char 




signed char* 
h 
short int 
unsigned short int 




short int* 
l 
long int 
unsigned long int 

wint_t 
wchar_t* 

long int* 
ll 
long long int 
unsigned long long int 




long long int* 
j 
intmax_t 
uintmax_t 




intmax_t* 
z 
size_t 
size_t 




size_t* 
t 
ptrdiff_t 
ptrdiff_t 




ptrdiff_t* 
L 


long double 




