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printf Type Field Characters

The type character is the only required format field; it appears after any optional format fields. The type character determines whether the associated argument is interpreted as a character, string, or number. The types C, n, p, and S, and the behavior of c and s with printf functions, are Microsoft extensions and are not ANSI compatible.

printf Type Field Characters

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 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 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.

Note   If the argument corresponding to %s or %S is a null pointer, "(null)" will be printed.

Note   In all exponential formats, the default number of digits of exponent to display is three. Using the _set_output_format function, the number of digits displayed may be set to two, expanding to three if demanded by the size of exponent.

Security Note   The %n format is inherently insecure and is disabled by default; if %n is encountered in a format string, the invalid parameter handler is invoked as described in Parameter Validation. To enable %n support, see _set_printf_count_output.

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