# Formatted Output
Formatted Output
# Formatted Output
* * *
**[Print Formats](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_prin.html#Print%20Formats)· [Print Functions](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_prin.html#Print%20Functions)· [Print Conversion Specifiers](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_prin.html#Print%20Conversion%20Specifiers)**
* * *
Several library functions help you convert data values from
encoded internal representations to text sequences that are
generally readable by people. You provide a
[format string](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_prin.html#format%20string) as the value of the
`format` argument to each of these functions, hence
the term **formatted output**.
The functions fall into two categories.
The **byte print functions**
(declared in
[``](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_stdio.html#<stdio.h>))
convert internal representations to sequences of type *char,*
and help you compose such sequences for display:
[fprintf](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_stdio.html#fprintf),
[printf](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_stdio.html#printf),
[sprintf](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_stdio.html#sprintf),
[vfprintf](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_stdio.html#vfprintf),
[vprintf](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_stdio.html#vprintf), and
[vsprintf](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_stdio.html#vsprintf).
For these function, a format string is a
[multibyte string](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_over.html#multibyte%20string)
that begins and ends in the
[initial shift state](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_charset.html#initial%20shift%20state).
The **wide print functions**
(declared in
[``](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_wchar.html#<wchar.h>)
and hence added with
**[Amendment 1](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_over.html#Amendment%201)**)
convert internal representations to sequences of type
[`wchar_t`](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_stddef.html#wchar_t),
and help you compose such sequences for display:
[fwprintf](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_wchar.html#fwprintf),
[swprintf](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_wchar.html#swprintf),
[wprintf](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_wchar.html#wprintf),
[vfwprintf](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_wchar.html#vfwprintf),
[vswprintf](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_wchar.html#vswprintf), and
[vwprintf](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_wchar.html#vwprintf).
For these functions, a format string is a
[wide-character string](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_over.html#wide-character%20string).
In the descriptions that follow, a wide character `wc`
from a format string or a stream is compared to a specific (byte)
character `c` as if by evaluating the expression
`wctob(wc) == c`.
## Print Formats
A **format string** has the same
syntax for both the print functions and the
[scan functions](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_scan.html#Formatted%20Input),
as shown in the diagram.
A format string consists of zero or more
**conversion specifications**
interspersed with literal text and
**white space**.
White space is a sequence of one or more
characters `c` for which the call
`isspace(c)` returns nonzero.
(The characters defined as white space can change when you change the
[`LC_CTYPE`](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_locale.html#LC_CTYPE)
[locale category](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_locale.html#locale%20category).)
For the print functions, a conversion specification is one of the
[print conversion specifications](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_prin.html#print%20conversion%20specification) described below.
A print function scans the format string once from beginning
to end to determine what conversions to perform. Every print
function accepts a
[varying number
of arguments](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_stdarg.html#varying%20number%20of%20arguments), either directly or under control of an argument of type
[`va_list`](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_stdarg.html#va_list).
Some print conversion specifications
in the format string use the next argument in the list.
A print function uses each successive argument no more than
once. Trailing arguments can be left unused.
In the description that follows:
- **integer conversions** are the
**conversion specifiers** that
end in `d`, `i`, `o`, `u`,
`x`, or `X`
- **floating-point conversions**
are the conversion specifiers
that end in `e`, `E`, `f`, `F`,
`g`, or `G`
## Print Functions
For the print functions, literal text or
[white space](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_prin.html#white%20space) in a format
string generates characters that match the characters in the format
string. A
**print conversion specification** typically generates characters
by converting the next argument value to a corresponding text sequence.
A print conversion specification has the format:
Support for fixed-point conversions is added with
the C Technical Report TR18037.
These closely match the extensions for the Freescale
Signal Processing Engine Auxiliary Processing Unit.
This [implementation](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_index.html#implementation)
also includes, as a conforming extension, conversions for
the vectors supported by the Freescale
**AltiVec** architecture.
Following the percent character (**`%`**)
in the format string, you can write an optional
**position**,
which consists of a nonzero decimal integer followed by a
dollar sign (**`$`**). If present, an
argument position with value `N` indicates
that at least `N` arguments to the print
function follow, all having the type required for the
conversion specifier. Argument number `N`,
counting from 1, is the one converted; no arguments are
skipped over. If no argument position is present, the
next argument to the print function has the type required
for the conversion specifier. It is converted and then
skipped over. (This implementation supports argument
positions as a conforming extension.)
Following any argument position, you can write zero or more
**format flags**:
- **`-`**
-- to left-justify a conversion
- **`+`**
-- to generate a plus sign for signed values that
are positive
- **`space`**
-- to generate a `space` for signed values
that have neither a plus nor a minus sign
- **`#`**
-- to prefix `0` on an `o` conversion,
to prefix `0x` on an `x` conversion,
to prefix `0X` on an `X` conversion,
or to generate a decimal point and fraction
digits that are otherwise suppressed on a floating-point conversion
- **`0`**
-- to pad a conversion with leading zeros after
any sign or prefix, in the absence of a minus (`-`)
format flag or a specified precision
For [AltiVec](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_prin.html#AltiVec) vector conversions,
you can intersperse format flags with an optional
**separator**, the characters
comma, semicolon, equal sign, or underscore. The conversion
occurs for each of the elements of the vector, and
generates a separator between each pair of elements.
If you specify no separator, the default is:
- for the `c` conversion specifier, no character.
- for all other conversion specifications, a space character.
Following any format flags, you can write a
**field width** that
specifies the minimum number of characters to generate for the conversion.
Unless altered by a format flag,
the default behavior is to pad a short conversion
on the left with `space` characters.
If you write an asterisk (**`*`**)
instead of a decimal number for a field width, then a print
function takes the value of the next argument (which must be of type
*int*) as the field width. If the argument value is negative,
it supplies a `-` format flag
and its magnitude is the field width.
Following any field width, you can write a dot (**`.`**)
followed by a
**precision**
that specifies one of the following:
the minimum number of digits to generate on an integer conversion;
the number of fraction digits to generate on an `e`,
`E`, or `f` conversion;
the maximum number of significant digits to generate
on a `g` or `G` conversion; or the maximum number
of characters to generate from a
[C string](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_over.html#C%20string)
on an `s` conversion.
If you write an **`*`** instead of
a decimal number for a precision,
a print function takes the value of the next argument (which must
be of type *int*) as the precision. If the argument value is
negative, the default precision applies. If you do not write either
an `*` or a decimal number following the dot, the precision
is zero.
## Print Conversion Specifiers
Following any
[precision](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_prin.html#precision),
you must write a one-character **print conversion specifier**,
possibly preceded by a one- or two-character qualifier.
Each combination determines the type required of the
next argument (if any) and how the library functions alter the argument
value before converting it to a text sequence.
The [integer](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_prin.html#integer%20conversions) and
[floating-point conversions](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_prin.html#floating-point%20conversions) also determine
what base to use for the text representation.
If a conversion specifier requires a precision *p* and you do
not provide one in the format, then the conversion specifier chooses
a default value for the precision.
In the descriptions that follow, array declarations for arguments
are not to be taken literally. A declaration of the form:
short x[8]Copy to clipboard
is shorthand for:
struct {short x[8]; }Copy to clipboard
And a cast of the form:
(short x[8])xCopy to clipboard
is shorthand for:
*(struct {short x[8]; } *)&xCopy to clipboard
The following table lists all defined combinations
and their properties:
Conversion Argument Converted Default Pre-
Specifier Type Value Base cision
%c int x (unsigned char)x
%lc wint_t x (wchar_t)x
%d int x (int)x 10 1
%hd int x (short)x 10 1
%ld long x (long)x 10 1
%e double x (double)x 10 6
%Le long double x (long double)x 10 6
%E double x (double)x 10 6
%LE long double x (long double)x 10 6
%f double x (double)x 10 6
%Lf long double x (long double)x 10 6
%g double x (double)x 10 6
%Lg long double x (long double)x 10 6
%G double x (double)x 10 6
%LG long double x (long double)x 10 6
%i int x (int)x 10 1
%hi int x (short)x 10 1
%li long x (long)x 10 1
%n int *x
%hn short *x
%ln long *x
%o int x (unsigned int)x 8 1
%ho int x (unsigned short)x 8 1
%lo long x (unsigned long)x 8 1
%p void *x (void *)x
%s const char *x (const char *)x large
%ls const wchar_t *x (const wchar_t *)x large
%u int x (unsigned int)x 10 1
%hu int x (unsigned short)x 10 1
%lu long x (unsigned long)x 10 1
%x int x (unsigned int)x 16 1
%hx int x (unsigned short)x 16 1
%lx long x (unsigned long)x 16 1
%X int x (unsigned int)x 16 1
%hX int x (unsigned short)x 16 1
%lX long x (unsigned long)x 16 1
%% none (char)'%'Copy to clipboard
The print conversion specifier determines any behavior not summarized
in this table. For all floating-point conversions:
- Positive infinity prints as `inf` or `INF`.
- Negative infinity prints as `-inf` or `-INF`.
- Not-a-number (NaN) prints as `nan` or `NAN`.
The upper-case version prints only for an upper-case conversion specifier,
such as `%E` but not `%Lg`.
In the following descriptions, *p* is the precision.
Examples follow each of the print conversion specifiers.
A single conversion can generate up to 509 characters.
You write **`%c`**
to generate a single character from the converted
value.
printf("%c", 'a') generates a
printf("<%3c|%-3c>", 'a', 'b') generates < a|b >Copy to clipboard
For a
[wide stream](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_file.html#wide%20stream),
conversion of the character `x` occurs as if by calling
`btowc(x)`.
wprintf(L"%c", 'a') generates btowc(a)Copy to clipboard
You write **`%lc`**
to generate a single character from the converted value.
Conversion of the character `x` occurs as if
it is followed by a null character in an array of two elements of type
[`wchar_t`](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_stddef.html#wchar_t)
converted by the conversion specification
[`ls`](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_prin.html#%ls).
printf("%lc", L'a') generates a
wprintf(L"lc", L'a') generates L'a'Copy to clipboard
You write **`%d`**,
**`%i`**,
**`%o`**,
**`%u`**,
**`%x`**, or
**`%X`** to generate
a possibly signed integer representation. `%d` or `%i`
specifies signed decimal representation, `%o`
unsigned octal, `%u` unsigned decimal,
`%x` unsigned hexadecimal using the digits `0-9`
and `a-f`, and `%X` unsigned
hexadecimal using the digits `0-9` and `A-F`.
The conversion generates at least *p* digits
to represent the converted value. If *p* is zero,
a converted value of zero generates no digits.
printf("%d %o %x", 31, 31, 31) generates 31 37 1f
printf("%hu", 0xffff) generates 65535
printf("%#X %+d", 31, 31) generates 0X1F +31Copy to clipboard
You write **`%e`** or
**`%E`** to generate
a signed decimal fractional representation with
a decimal power-of-ten exponent. The generated text takes the form
*±d.dddE±dd,* where *±* is either a plus or
minus sign, *d* is a decimal digit, the decimal point (*.*)
is the decimal point for the current
[locale](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_locale.html#locale),
and *E* is either `e` (for `%e` conversion)
or `E` (for `%E` conversion).
The generated text has one integer digit,
a decimal point if *p* is nonzero or if you specify the `#`
format flag, *p* fraction digits, and at least two exponent digits.
The result is rounded. The value zero has a zero exponent.
printf("%e", 31.4) generates 3.140000e+01
printf("%.2E", 31.4) generates 3.14E+01Copy to clipboard
You write **`%f`**
to generate a signed decimal fractional representation
with no exponent. The generated text takes the form *±d.ddd,*
where *±* is either a plus or minus sign,
*d* is a decimal digit, and the decimal point (*.*)
is the decimal point for the current
[locale](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_locale.html#locale).
The generated text has at least one integer digit,
a decimal point if *p* is nonzero or if you specify
the `#` format flag, and *p* fraction digits.
The result is rounded.
printf("%f", 31.4) generates 31.400000
printf("%.0f %#.0f", 31.0, 31.0)generates 31 31.Copy to clipboard
You write **`%g`** or
**`%G`** to generate
a signed decimal fractional
representation with or without a decimal power-of-ten exponent, as appropriate.
For `%g` conversion, the generated text
takes the same form as either `%e`
or `%f` conversion. For `%G` conversion,
it takes the same form as either
`%E` or
`%f`
conversion.
The precision *p* specifies the number
of significant digits generated. (If *p* is zero, it is changed
to 1.) If `%e` conversion would yield an exponent in the range
[-4, *p*), then `%f` conversion occurs instead.
The generated text has no trailing zeros
in any fraction and has a decimal point
only if there are nonzero fraction digits, unless you specify the
`#` format flag.
printf("%.6g", 31.4) generates 31.4
printf("%.1g", 31.4) generates 3.14e+01Copy to clipboard
You write **`%n`**
to store the number of characters generated
(up to this point in the format) in an integer object
whose address is the value of the next successive argument.
printf("abc%n", &x) stores 3Copy to clipboard
You write **`%p`**
to generate an external representation of a *pointer to void.*
The conversion is implementation defined.
printf("%p", (void *)&x) generates, e.g. F4C0Copy to clipboard
You write **`%s`**
to generate a sequence of characters from
the values stored in the argument
[C string](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_over.html#C%20string).
printf("%s", "hello") generates hello
printf("%.2s", "hello") generates heCopy to clipboard
For a
[wide stream](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_file.html#wide%20stream), conversion
occurs as if by repeatedly calling
[`mbrtowc`](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_wchar.html#mbrtowc),
beginning in the
[initial conversion state](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_charset.html#initial%20conversion%20state).
The conversion generates no more than *p* characters,
up to but not including the terminating null character.
wprintf(L"%s", "hello") generates helloCopy to clipboard
You write **`%ls`**
to generate a sequence of characters from
the values stored in the argument
[wide-character string](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_over.html#wide-character%20string).
For a [byte stream](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_file.html#byte%20stream),
conversion occurs as if by repeatedly calling
[`wcrtomb`](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_wchar.html#wcrtomb), beginning in the
[initial conversion state](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_charset.html#initial%20conversion%20state),
so long as complete multibyte characters can be generated.
The conversion generates no more than
*p* characters, up to but not including the terminating null
character.
printf("%ls", L"hello") generates hello
wprintf(L"%.2s", L"hello") generates heCopy to clipboard
You write **`%%`** to generate
the percent character (`%`).
printf("%%") generates %Copy to clipboard
* * *
See also the
**[Table of Contents](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_index.html#Table%20of%20Contents)** and the
**[Index](https://docs.qualcomm.com/doc/80-N3040-23/topic/_cpp_index.html)**.
*[Copyright](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_crit_pjp.html) © 1992-2006by P.J. Plauger and Jim Brodie. All rights reserved.*
Last Published: Oct 06, 2026
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